The futures and Forex markets empty the accounts of thousands of traders every year. For most entering trading, and this is true for over 90%, trading commodities means a very certain financial death.

The markets are ruthless and will send people home empty-handed without a care.

The opportunities for making money are numerous, and the leverage entices so many people to jump in head first, that it is unreal. It is the ultimate, white collar get-rich-quick arena.

Unfortunately, like all other areas that the get-rich-quick opportunities are being sold, the ratio of losers to winners is absolutely horrific.

First thing to do to avoid being one of the carcasses left on the battlefield is to realize that trading is not for everyone. It is definitely not for the squeamish or weak of heart. You’ve got to have resources and a backbone of steel.

Secondly, realize that it does take knowledge. If it were that easy to make millions in the markets, don’t you think that it would be saturated with people by now? Just like any other business endeavor, you have to have a clue as to what you’re doing. No one is standing at the gates with a bag of money to hand you, just because you showed up. You actually do have to “earn” your fortune here.

Third, recognize that it takes skill. For every opportunity to make money in trading, there are ten ways to lose it. There are several skills necessary to spot the opportunities, but more importantly the skills to plan worthwhile trades and then to properly execute them to show a profit at the end of the month.

You have to first know what skills to develop, and then have the fortitude to actually develop those skills and put them into practice. Too many people want to ignore this part and just go straight to collecting the profits without any effort.

Fourth is to expand your awareness. Get past the greed factor that pressures you into wishing every trade to be that home run that let’s you retire this month. If you want this to be a profit center for years to come, then treat it as such: long term. Get your focus on doing it right the first time around through preparation, learning and a long term focus.

The other aspect of awareness is self-awareness. Make sure that you’re trading with a system that matches your emotional style. You wouldn’t get into an occupation that disagreed with your natural tendencies and desires would you? Would you take a job that required 80% travel if you hated to travel? NO! The only way to trade successfully for the long term and enjoy the process is to be aware of your own tendencies and desires, and use a strategy and system that are in alignment with who you are as a person.

Most importantly, you’d better be trading with true risk capital. If you’re trading with “scared” money, that is money that you really can’t afford to lose, then your days as a trader are numbered. You’d probably be better off quitting right now and taking home whatever is in your account.

The stock markets have crashed and recovered and then crashed again. Similarly for commodities like silver and gold. The overall trend for silver and gold is positive though . Also stock market indices too over the years look positive. But that's an index, only if you buy the right stocks do you get the benefit. Essentially the risks, with an investment like stocks, are huge. Moreover less risky instruments like Mutual Funds have huge entry and exit fees.

Real Estate is the one investment from which you can get a steady income, and at the same time enjoy a steady appreciation. This specially holds good if you buy apartments close to IT parks, railways/metro stations in any big city, close to any place of commercial or industrial activity. A rental income is an assured monthly income with little hassles, all things going right.

It's also a usable investment. You can feel it, touch it, live in it, rent it out.

Currently real estate prices are increasing literally on a daily basis. This is definitely not a trend that is sustainable. If you plan to realistically invest in the real estate market, please ensure that you have a timeframe of a few years. The current real estate increases are hugely attributed to the buying power of IT professionals and their willingness to pay a premium for any piece of property. Places like Kerala too have show steep escalations and the main reason is the money flowing in from the Middle East. Even though Keralites believe that the land prices there are now higher than what they should be, on comparing to cities like Bangalore, Kerala is still very under priced. Similarly for Pune. Land prices in Pune are seriously undervalued compared to Bangalore. In 2005 you could purchase land in Kondhva for around 300 Rs per sq feet and land in Bhugaon close to the IT Park for 400 Rs per sq feet. The prices have increased a 100% within a year. It's still cheap compared to Bangalore !!

High incomes of IT employees, a bull run on the stock market and foreign repatriations have made the Indian real estate market a little volatile at this point. But a country with a billion people and still growing will always have a housing issue, and any investment in the housing market can never go wrong. Real estate; whether land or houses will always sell at a premium.

For most people who live in 3 storeyed apartments that are over 20 years old, builders have offered schemes where current apartment owners sell the land and building to the builder, in return for a bigger apartment. The builder constructs a high rise there and recovers his cost from the fact that in a building where there were 12 apartments, there are now 60. This is a win-win situation. Builders get prime land in the city and the apartment owners get an upgraded apartment that has a lot more market value.

Rents too have been on the increase. Apartments close to work places or transportation hubs rent well. Since most tenants are professionals, owners need not worry about tenants staying for long periods and then refusing to vacate.

Interest rates in India are much much higher than in the US. There it's about 6%, we're close to 9%. Realistically you can expect property to appreciate between 10-15% every year. Holds true more for land. For housing the property price increase usually depends on increase in costs of raw material like steel and cement.

Do not always look at real estate just as an investment. A house is always a great place to live in. For first timers, do not look at real estate as an investment, but a home to go to.

The leading manufacturers that are spread throughout the nation supply welding machines and other spare parts used in welding through their shops and retails stores. WeilerDirect.com is a supplier of Lincoln and Hobart welding machines and other accessories like welding helmets.

Hobart supplies spot welders, oxy-acetylene torches, spot welders, resistance spot welders, and welders/generators are offered. Lincoln supplies MIG welders, titanium, aluminum, stainless steel, tool steel, and cold rolled steel. Control systemizing supplies weld master machines that are useful in laser welding. With the usage of argon shield, the carbon dioxide laser welding technique is useful for achieving precision and accuracy.

J&R Welding Supply Corporation is the supplier for Hobart, Smith &Victor, Thermal Dynamics welding machines, and other accessories. They supply industrial gas and hydro testing equipment like victor medial kits, helium regulators, hoses, strikers, torches, TIG guns, antispatters, electrodes, solid wire, tubular wire, cylinders, hammers, brushes, trucks.

ESAB Group Inc. supplies TIG welders, MIG or wire welders, stick welders, flux cored welders, multi process welders, plasma arc cutters, wire feeders, multi operator systems, and automated welding systems. ESAB also produces submerged arc welders, welding equipment, welding guns and accessories, oxy-fuel torches, gas torches, gas regulators, gas welding tips and nozzles, stainless steel welding wire, flux cored welding wire, MIG welding wire, welding consumables. They also supply welder training materials for the industrial, maintenance & repair, farm and ranch, construction, motor sports, hobbyist and fabrication markets. All the ESAB products can be ordered and purchased online. ESAB Group Inc. and its subsidiary units in Atlanta, Hanover, Ashtabula, Ohio, Florida, Monterrey, and South California have won the ISO 9002 certification.

Hydroweld specializes in underwater welding equipments and they undertake projects also. Hydroweld is operating its branches in the US, Netherlands, Australia, South Africa, China, Korea, Sweden and Thailand, and supply underwater welding equipment. Seelye, Inc. is unique in its supply of thermoplastic hot air welding equipment.

Manufacturing sector is an area where investment opportunities exist. Initially developed under the import substitution policy, there has now been a shift to export oriented manufacturing as the thrust of Kenya's industrial policy. The sector plays an important role in adding value to agricultural output and providing forward and backward linkages, hence accelerating overall growth.

The manufacturing sector now comprises of more than 700 established enterprises and employs directly over, 218,000 persons as at the year 2000. A wide range of opportunities for direct and joint-venture investments exist in the manufacturing sector, including agro-processing, manufacture of garments, assembly of automotive components and electronics, plastics, paper, chemicals, pharmaceuticals, metal and engineering products for both domestic and export markets.

Paper Products

Kenya has an integrated pulp paper mill plant producing paper and paper board from renewable forest products. However, the country imports coated white lined chipboard and other boards for packaging, newsprint, printed paper and other types of paper. Investment opportunities exist in the production of paper from other raw materials such as bagasse, sisal waste, straw and waste paper.

Textiles and Apparels
Textile, Garment and Apparel manufacturing has a very high potential in Kenya. The basic raw material inputs such as dyes and chemicals are imported, as are all textile equipment and most spare parts. Investment opportunities exist under the Manufacturing Under Bond scheme and in the Export Processing zones for the production of items such as yarn and garments.

Metal and Engineering Works

Kenya has a basic metal sector making a variety of downstream products from local and imported steel scrap, steel billets and hot rolled coils. Kenya imports steel billets, coils, wire rod and wires, steel plates, sheets, steel scrap and pig iron. The country possesses a broad-based metal products sector with various independent engineering, foundry and metalwork workshops. Opportunities exist in the development of a nucleus foundry making precision castings that are then processed into precision components.

Vehicle Parts and Assembly

The motor vehicle component industry is rapidly developing to supply the needs of a few motor vehicle assemblers to meet certain local content requirements. Opportunities exist for manufacture of components for use by local assemblers for domestic market and for export to regional markets.

Electrical Equipment

Investment potential exists for the production of motors, circuit breakers, transformers, switch gears, irrigation pumps, capacitors, resistors, insulation tapes, electrical fittings and integrated circuit boards for both the domestic and export markets.

Electronics
Although Kenya's electronic industry is still at its infancy, a number of firms in the assembly, testing, repair and maintenance of electronic goods are in operation and are rapidly increasing their scope of activities to meet the growing demands of the industry.
Key opportunities for direct investments, joint-ventures and subcontracting exist in assembly of a wide range of electronic goods in Kenya, especially within the Manufacturing Under Bond scheme and Export Processing Zone Programmes.
These include the production of:

• Consumer electronics, such as colour televisions, Video Cassette Recorders (VCRs), printers, floppy disk drives and Compact Disk Roms (CD-Rs);
• Telecommunication equipment, such as printed circuit boards, and transmission equipment; and
• Support items such as cables, cords, die casting and metal plating.

With a labour force which is well-equipped to meet the labour skill requirements for the industry and the relatively large domestic and export market potential of electronics in the region, Kenya offers an enormous potential for the manufacturing and assembly of electronic items.

Plastics, Chemicals and Pharmaceuticals

The plastics industry in Kenya is well-developed and produces goods made of polyvinyl chloride (PVC), polythylene, polystyrene, and polypropylene. All materials are imported in the form of granules.

A large number of pharmaceutical formulations are produced locally in the form of tablets, syrups, capsules, and injectables, but the bulk of pharmaceuticals is imported. There is room for additional investment in the pharmaceutical industry.

Many attractive investment opportunities in chemicals, pharmaceuticals and fertilizers remain unexploited. These include the production of PVC granules from ethyl alcohol; fomaldehyde from methanol; melanine and urea; mixing and granulating of fertilizers; cuprous oxychloride for coffee bean disease; caustic soda and chlorine based products; carbon black; activated carbon; precipitated calcium carbonate; textile dyestuff; ink for ball-point pens; and gelatine capsules.
Mining and Mineral Products
Opportunities exist in the production of glass as the country is not self-sufficient. A few manufacturing units produce ceramic pottery and tiles, however, substantial quantities of ceramic pottery, tiles, sanitary-ware, and insulators are imported. Investment potential exists in prospecting and mining of other minerals such as gold, precious stones and petroleum.

Wood and Wood Products
Making use of renewable resources, investment opportunities exist for production of high quality and hand carved furniture for export, high density board from saw dust for the domestic market, high quality veneers, wooden toys, sporting goods such as cricket bats and rackets for export, and other specialty items. Recognizing the importance of environmental preservation, the Government pursues an active re-afforestation programme.

Background

Originally molybdenum was confused with graphite and lead ore, and was not prepared till 1782 by Hjelm in the impure state. Molybdenum does not occur native, and is obtained mainly from molybdenite (MoS2). Other minor commercial ores of molybdenum are powellite (Ca(MoW)O4) and wulfenite (PbMoO4). It may also be recovered from copper and tungsten operations as a by-product.

The metal is prepared from the powder made by the hydrogen reduction of purified molybdic trioxide or ammonium molybdate. Molybdenum the metal is silvery-white, and very hard. However, it is softer and more ductile than tungsten and is readily worked or drawn into very fine wire. It cannot be hardened by heat treatment, only by working. It exhibits a high elastic modulus and a very high melting point. Above temperatures of 760°C (1400°F) molybdenum the metal forms an oxide that evaporates as it is formed and its resistance to corrosion is high. It has a low thermal expansion and its heat conductivity is twice that of iron. It is one of the few metals that has some resistance to hydrofluoric acid.
Key Properties

Molybdenum is a refractory metal typically used in high temperature applications. Key properties include:

· Low co-efficient of thermal expansion (5.1x10-6 m/m/°C) which is about half that of most steels

· Good thermal conductivity

· Good electrical conductivity

· Good stiffness, greater then that of steel (Young’s Modulus 317MPa)

· High melting point (2615°C)

· Good hot strength

· Good strength and ductility at room temperature

· High density (10.2 g/cm3)

Its ability to withstand high temperatures and maintain strength under these conditions are responsible for the fact that molybdenum finds most of its application at elevated temperatures. In fact, it can work at temperatures above 1100°C (in non-oxidising conditions), which is higher than steels and nickel-based superalloys.

When exposed to temperatures in excess of 760°C in air rapid oxidation can result. Under these conditions, the oxide layer sublimes and the base metal is attacked. Thus, molybdenum performs best in inert of vacuum environments.
Applications
Molybdenum Metal

Molybdenum metal is used in:

· Alloying agent – contributing hardenability, toughness to quenched/tempered steels. It also improves the strength of steels at high temperatures (red-hardness).

· In nickel-based alloys (such as Hastelloys®) and stainless steels it imparts heat-resistance and corrosion-resistance to chemical solutions.

· Electrodes for electrically heated glass furnaces and forehearths.

· Nuclear energy applications, as missile and aircraft parts (where high temperature resistance is vital).

· As a catalyst in the refining of petroleum.

· As a filament material in electronic/electrical applications.

· As a support members in radio and light bulbs.

· Arc resistant electric contacts.

· Thermocouple sheaths

· Flame- and corrosion-resistant coatings for other metals (generally arc deposited for metallising).
Molybdenum Compounds

Molybdenum and its compounds are used in:

· Molybdenum sulphide and selenites are used as a high temperature lubricant in favour to petroleum based oils, due to its superior high temperature resistance.

· Sodium molybdate (Na2MoO4) in the anhydrous form is used as a dry powdered fertiliser.

· Calcium molybdate (CaMoO4), Molyte, molybdic oxide, molybdenum-chromium are used as sources of molybdenum for steels.

Background

Microtex is Fibretech’s range of metal fibres, filaments and mats for applications in materials reinforcement, sound absorption, filtration, catalytic media and friction products.
Advantages of Mictotex Metal Fibre Products

· Allows uniquely tailor-made to meet your needs

· Greater choice and increased performance from alloys now available in stainless steels, nickel alloys, copper alloys, aluminium alloys and iron-chrome-aluminium alloys.

· As much or as little as you need - batch production from a few kilos to a thousand tonnes.

· Performance advantages over old technology ‘wire wool’ type of materials.

· Wider range of finished forms - now available in semi-continuous mats or fibres in a variety of lengths down to 1mm.

· Enhanced corrosion resistance

· Beneficial physical properties only available from the unique direct cast rapid solidification process.
Manufacture of Microtex Materials

Fibretech Microtex is an all-new product manufactured by a process unique to Fibre Technology Ltd - the 4th generation direct cast process patented as “melt overflow”. Rapid solidification of the metal alloys, with cooling rates of over 10K/second, produces refined microstructures and minimal segregation with improvements over traditional forms in mechanical, chemical, electrical and magnetic properties.
Advantages of Direct Casting Techniques

Direct casting is a highly efficient process and introduces significant cost advantages over ‘wire’ type products manufactured by traditional methods.
Microtex Materials in Aggressive Environments

Fibretech Microtex products in nickel based alloys can provide solutions to many problem areas not previously considered possible. As filtration media, by varying the diameter and packing density of fibres and filaments, a wide range of new characteristics can be achieved. Bonding at intersections produces rigid structures. Fibretech stainless steel fibre filter materials offer high temperature capability and resistance to highly corrosive environments.
Microtex in Metal Matrix Composites

Fibretech Microtex in fine metal fibre form dispersed within a lower melting point alloy matrix creates a composite with significantly enhanced tensile strength and toughness properties. An example would be nickel alloy fibres dispersed in aluminium. Fibre preforms can be placed in mould cavities and, as the component is cast, molten metal infiltrates the fibres resulting in localised areas of reinforcement. Typical applications would be the crown and gudgeon pin locations in pistons saving both weight and cost.
Iron - Chrome - Aluminium Alloys

Fibretech’s direct cast technique produces this with high aluminium content in filament, fibre, ribbon and strip formats, all of which have excellent high temperature oxidation resistance compared with an alloy of equivalent chromium content. The alumina surface provides the necessary compatibility for catalysation,
Process Flexibility Leads to Tailorable Compositions and Forms

Fibre Technology’s unique process introduces the facility for customers to create products developed specifically to meet their precise needs. This flexibility combined with the wide choice of form is providing breakthroughs for both existing and new applications. For example, in the automotive industry there has been a rapid take-up of Fibretech Microtex products in silencer fillings and friction materials. In other industries it can be used in seal and gasket composites for reinforcement in plastic, ceramic and metal matrix products.
Microtex in Automotive Applications

Microtex is now providing solutions in automotive applications, where high temperatures or corrosion can cause problems for conventional materials. Acoustic packings for exhaust systems now face far higher gas temperatures and there is demand for longer and longer design lives. Traditional sound absorbing materials such as glass fibre and basalt fibre are unable to stand the strain and, today, even 434 grade stainless steel wire wool is at the limit of its oxidation resistance. Fibretech Microtex 446 grade mat out performs these materials while providing a cost effective solution.

In brake pads traditional chopped mild steel wire wool reinforcement can, in some circumstances, corrode and cause catastrophic situations. Stainless steel fibres do provide a solution but, until Microtex appeared on the market, these have been considered to be prohibitively expensive. The cocktail of metals used in friction applications includes brass and copper. In the past manufacturers have had to compromise and use either powder or chopped swarf. Now Microtex offers these materials in the ideal fibre shape providing an important technological and cost saving breakthrough.

Background

Microtex HT is Fibretech’s lightweight acoustic absorption material for automotive exhaust silencers. Made from semi-continuous stainless steel filaments using Fibretech’s unique Rapid Solidification (RS) technology, HT outperforms conventional glass, basalt and steel alternatives at high temperature.

Figure 1. Microtex HT in automotive exhausts and mufflers.

Unique Benefits of Microtex HT

· RS metallurgy

· No impurities

· Robust steel matrix

· “As-cast” ductility

· Enhanced sound absorption

· Homologation

· Customising

· Low cost

· Innovative, new alloy thermally stable to 1100°C

· Resistant to chemical corrosion

· Will not compact under gas pressure.

· Easy component manufacture.

· Can be combined with basalt or E-glass.

· Proven and accepted by vehicle and exhaust manufacturers.

· Optional “tailored” alloys possible.

· Suits all models.

Quality Guarantee

Microtex exhaust system fibres are made to ISO 9002 standards, conform to current safety and environmental standards, and are supported by a full in-house Technical Support Team.

Compositional and Design Flexibility

Other RS alloys can be manufactured on request to provide exhaust system designers with infinite variations for optimising performance and cost objectives

Wheeling-Pittsburgh Steel Corporation began using a new metallic heat exchanger on its No. 1 Blast Furnace on April 12. The device, which pre-heats blast gas used in the operation of the blast furnace, is expected to reduce the consumption of coke by about 3,000 tons per month. The $4 million heat exchanger is expected to pay for itself in coke savings during the first two months of its operations. The installation of a metallic heat exchanger is a first-of-its-kind application in the steel industry.

"The heat exchanger uses surplus blast furnace gas to increase the temperature of the blast gas to the furnace by 350 degrees," said Harry Page, Vice President, Engineering, Technology and Metallurgy. "While it is a fairly simple concept, it has never been used in the steel industry before and will result in a reduction in our coke usage at a time when coke is selling at record high prices."

Page notes that the concept was developed internally by the company's blast furnace operations department.

"The concept was initiated within blast furnace operations and further developed in cooperation with our engineering group," said Page. "Installation was completed within five months of project approval, which is a remarkable accomplishment."

Aker Kvaerner E&C developed the Wheeling-Pittsburgh Steel concept into a final design. Alstom provided the heat exchanger and Chapman Corp. performed the installation.

Hot blast for blast furnaces is normally preheated in refractory stoves, using blast furnace gas as a fuel source. In the case of the new metallic heat exchanger, a portion of the blast is heated in this new unit. The corresponding reduction in air flow through the refractory stoves allow the blast from the stoves to increase in temperature, effecting an overall increase in hot blast temperature to the furnace.

Background

The effects of residual and applied stresses and corrosive environments in service are closely interrelated. The more highly stressed (higher energy) regions of a metal will become anodic and corrosive cells will be set up due to differences in local stress levels. Cold worked regions, for example tube or sheet bends and cut edges, will be corroded in preference to uniform parts of sections in the same way that grain boundaries are attacked more than grain interiors on the microscopic scale.

Stress Corrosion Cracking (SCC) Defined

The combined effects of stress and corrosion can result in a special type of failure known as Stress Corrosion Cracking (SCC). This arises under a particular set of circumstances for a given alloy: specific alloy condition plus specific corrosive media and sufficient local tensile stress. Chloride induced cracking of stainless steels, caustic cracking of plain carbon steels and ammonia damage to copper alloys are typical examples of this problem. The mechanism of SCC is shown as a simple representation in Figure 1.

Figure 1. Schematic view of Stress Corrosion Cracking (SCC) and corrosion fatigue cracking

SCC is believed to be nucleated at pitting damage sites and develops under the action of local tensile stresses as a highly branched network of fine cracks. At each crack tip the combined action of the tensile stress and specific ions in the corrosive media cause continual crack propagation with little evidence of local deformation.

In austenitic stainless steels, for example, warm chloride solutions in the presence of residual tensile stress can lead to cracking. SCC tendency is slight in low Ni ferritic and martensitic grades but is severe in the 8-10% Ni austenitic steels. Duplex stainless steels have greater SCC resistance than austenitic since the duplex microstructure helps to inhibit the growth of SCC cracks, which tend to be deflected or arrested at austenite-ferrite interfaces. Maximum resistance is obtained with 50/50 austenite-ferrite microstructures and the dispersion of the two phases should be as fine as possible. The increased interest in the duplex grades stems not only from their high pitting and SCC resistance but also from their higher proof stress level which offers savings in material and weight over austenitic material.

When does SCC occur?

Stress corrosion cracking presents an especially difficult problem, since not only is it highly localised but it can occur in environments that are merely mildly corrosive to the material. The damaging concentration of the harmful ions in that environment may be quite small and difficult to detect and, even in the absence of applied stress, residual stresses in a structure can often be of a sufficiently high level to cause SCC and failure in service.

In a given situation the time of exposure needed to cause SCC failure depends on the stress intensity at any pre-existing or developed crack tip. The concentration of stress at the tip of a sharp crack or flaw can be quantified in terms of the Stress Intensity Factor, K₁. It determines the growth rate of SCC cracks for a specific alloy environment combination. Catastrophic failure of a component will occur when this factor reaches a critical value, the Fracture toughness of the material, K_1C. This enables the determination of allowable defect size in design to avoid failure under given loading conditions.

In stage 2, the crack growth rate is independent of K₁ and depends instead on the corrosive environment and temperature. During stage 2 growth, K₁ continues to increase and this leads to the rapid acceleration of the crack in stage 3, and final fast fracture when K₁ reaches K_1C which is the Fracture Toughness of the material.

The higher the value of K_1SCC under given conditions, then the greater is the expected SCC resistance, but some materials do not appear to have a threshold resistance.

Background

An important aspect in the use of cathodic protection of reinforced concrete is the need for regular monitoring of performance and maintenance of the anode and electrical systems. This is to ensure protection and to prolong the life of the anode system. The power supply should be checked regularly to ensure that ac power is being supplied to the transformer-rectifier, and that dc current is being passed to each anode zone.
Performance Monitoring

Performance monitoring is typically undertaken at intervals of 3 to 6 months, to include the recording of zone current and voltage and potential steel/concrete. Where necessary, adjustments are made to ensure that protection is provided at the optimum level. Usually every 12 months, this monitoring is extended to a detailed visual inspection of the electrical system and the conductive coating anode to confirm their integrity and to identify any maintenance requirements.
The Conductive Coating Anode

The conductive coating anode is one of the most widely used and established anode systems for cathodic protection to reinforced concrete structures. This type of anode system has been successfully applied world-wide on a variety of structures including motorway viaducts, carparks, commercial and industrial buildings. It is cost effective and relatively easy to maintain. It is estimated that in the UK alone in excess of 150,000 square metres of reinforced concrete have been protected using conductive coating anode based cathodic protection systems.

The rate of deterioration of this type of anode is directly related to the current density. Acidic products are evolved at the interface between the coating and the concrete surface and will attack either the cement paste or the coating, leading to flaking and loss of bond. However, these effects can be significantly reduced by a proper design and zoning of the system and operation at current density levels sufficient to control corrosion, but no more, i.e. not over-protected.
Operating Criteria

It is recommended that commissioning of CP systems should start at a low level of current density for the initial part of the commissioning period to avoid any adverse effects on the anode durability. Intermediate tests can be then carried out, typically 14 days after energising, to determine what adjustments are needed to satisfy the operating criteria. Various criteria for ensuring satisfactory protection of the reinforcement have been considered for reinforced structures. The draft European standard for the cathodic protection of steel in atmospherically exposed concrete (pr EN 12961-1) proposes the following:

“For any atmospherically exposed structure, any representative point shall meet any one of the criteria given in items a) to (c.

a. An instant-off potential (measured between 0.1s and 1s after switching the dc circuit open) more negative than - 720mV with respect to Ag/AgCl/0.5MKCl.

b. A potential decay over a maximum of 24h of at least 100mV from instant-off.

c. A potential decay over an extended period (typically 24h or longer) of at least 150mV from the instant-off subject to a continuing decay and the use of reference electrodes (not potential decay sensors) for the measurement extended beyond 24 hours.”

A virtue of b) or c) is that the decay is independent of the nature of the reference electrode used or any variation in its absolute potential in the long term.

Historically it has been common to use a decay period of 4 hours although it should be noted that other intervals (such as 24 hours) might be suitable depending on the nature of the structure and surrounding environment.

When current is applied to the anode system there will be an associated error in potential measured between the reference electrode and the steel termed the IR drop. The current must therefore first be switched off to obtain the true fully polarised potential of the steel, termed the instant-off potential. However, the steel will depolarise shortly after with a characteristic exponential decay curve .

In order to obtain an accurate measurement of decay, the instant-off potential must be measured within a very short time window, typically 0.1 to 0.4 seconds after the current is switched off. The reinforcement will continue to depolarise and the potential decay is measured after a period of 4 hours (or other suitable intervals) from switch off. The accurate measurement of the instant-off potential is essential to determine the value of potential decay.

A further requirement of the operating criteria is that no instant-off potential more negative than -1100mV with respect to Ag/AgCl/0.5MKCl is permitted, to avoid the possibility of hydrogen evolution which may cause embrittlement of sensitive steels.

However, it is most unlikely that these levels of potential will be reached in a properly operated system.

The performance monitoring should thus be designed to ensure that the steel is polarised to the correct level of potential to achieve protection, but not excessively so.
Monitoring of Condition and Performance

The following routine investigations and monitoring are normally carried out:

· Visual check of each transformer-rectifier (or power supply)

· Measurement of current and voltage for each anode zone

· Visual check of the system from accessible locations (typically on a monthly basis)

· Potential decay at embedded reference electrodes (typically on three or six monthly basis depending on the stability of the system)

· Potential decay at embedded reference electrodes and paint free reference windows (if used) and a detailed close visual inspection (typically annually)

The surveys and results are recorded on proforma suitably designed for each task. Each task can either be associated with a transformer-rectifier, a particular structure or an anode zone. Each proforma acts as a checklist for the inspector so that important aspects of the repetitive task concerned are not overlooked.
Regular Visual Inspections

For installations that are exposed to harsh environments and/or vandalism such as those fitted to urban motorway structures it may be necessary, typically at monthly intervals, to perform the following inspections and tests and record their data on the proforma as mentioned above:

a. Visual examination and condition assessment of the transformer-rectifier (internal and external) including maintenance checks of: heater, thermostat, lighting, (where applicable) supply, timers, circuit breakers, supply points, general cabinet condition and security. Measurement of output current and voltage of each zone to confirm that each unit is operating correctly. The temperature and general weather conditions are recorded using keywords such as sunny, overcast, cloudy.

b. Visual examination and condition assessment from a point of easy access (i.e without special access provision) of the CP installation including the cable trays, conduit, junction boxes (where applicable), the primary anode conductor and the conductive coating comprising the anode system for evidence of deterioration, corrosion or damage. Any leakage affecting the structure is also recorded.

Occasional Monitoring

Typically at 3 or 6 monthly intervals (in some cases at 12 monthly intervals) depending on the stability of the system, the following tasks are performed in addition to the regular monitoring (above).

· Potential measurements at embedded reference electrodes (namely "current on", "instant off" and potential decay to 4 or 24 hours and longer periods if required);

· Adjustments to the applied currents, where necessary, are performed to ensure that a minimum current, consistent with ensuring adequate protection, is applied. The decision process for the current adjustments is as follows:

· A reduction in current where "instant off" potentials are more negative than -1000 mV with respect to Ag/AgCl/0.5MKCl reference electrode;

· A reduction in current where the current density is greater than 20mA/sq.m of concrete surface; (the maximum for long term operation of conductive coating anode systems);

· A reduction in current where the potential decay is significantly greater than 100mV (see note below);

· Where compatible with item i) and ii) above, an increase in current where the potential decay is less than 100mV (see note below).

· The alterations to the current at any particular occasion are normally limited to a maximum of 20% of the value before adjustment.

· NOTE: Items (iii) and (iv) only give a general guidance on the level of adjustments required. Other factors should be also considered such as potential readings at window locations, history and future anticipated performance of the system, present and future forecast weather and temperature.

· Zone output currents and voltages and “current on” steel/concrete potentials are re-measured and recorded following adjustments.
Major Inspection and Monitoring

In addition to the detailed inspection and monitoring undertaken, outlined above, the following tasks are performed typically on an annual basis:

· Detailed close visual inspection of the structure for evidence of deterioration or damage on the items listed in “Regular Visual Inspection” above (normally requiring access provision). Particular attention is given to areas of delamination, spalling, cracking, paint loss/flaking, rust spots/staining/streaking and other visual defects. Any areas of delamination and/or spalling are marked, measured and recorded;

· Potential measurements (namely “current on”, “instant off” and “decay” at all paint free reference windows in the paint anode system);

· The data from the monitoring is analysed and the performance of the CP system (for the whole year) is evaluated to identify required actions;

· The inspection record forms are examined and any maintenance requirements identified.
Maintenance

Any faults or defects identified in the cathodic protection or monitoring system as a result of the monitoring and/or inspections described above are repaired within a time scale consistent with the degree of urgency/condition assessment recorded in “Regular Visual Inspection” (mostly within the routine maintenance requirements for the structure).

A typical conductive coating anode system comprises primary anode conductors (wires or strips of coated titanium or niobium) and a conductive coating often overcoated with a compatible protective/cosmetic top coat.

Evidence from extensive site trials and full scale installations have demonstrated that major maintenance to the anode system which would involve large repair areas is not expected until at least 10 years operation. Minor repairs have been carried out earlier. However, in most cases to date, the defects have been attributable to outside factors (e.g. intense local wetting and/or ponding) or to isolated corroded metallic objects (tie wires or similar “rogue” steel from the construction phase) in the concrete surface, rather than a lack of performance or failure of the anode system.

Briefly the maintenance repair to the damaged concrete (from the effects of “rogue” steel) and anode system can be carried out as follows:

· Concrete and conductive coating anode damage due to "tie wires"

· Any remaining metal and existing damaged concrete are removed and repaired using appropriate repair mortar. In most cases the depth of concrete breakout necessary for this type of repair is less than 10 mm. The repairs are then allowed to cure and dry before the conductive anode paint is applied.

· Conductive anode coating and top coat deterioration

· Prior to coating application the new concrete areas and other areas where there is paint deterioration are normally prepared by local abrasion of the concrete surface using hand or power wire brush or grit blasting as appropriate to the area being repaired. Sufficient surface preparation is necessary to achieve a sound, clean, dust free surface to ensure a suitable base for a good physical bond for the conductive paint. In order to achieve sufficient electrical continuity between the existing and new conductive coating anode, the abrasive cleaning must be extended to create a sufficient overlap with the adjacent sound coating by removing a minimum of 50 mm of any decorative top coat around each repair area. Alternatively, the repaired area should be in sufficient electrical contact with existing or additional primary anode conductors.

· Following the curing of the conductive coating anode, the conductivity between the new and the surrounding existing conductive paint anode is tested at appropriate locations. Following the confirmation of sufficient electrical conductivity the decorative / protective topcoat is then applied.

· Primary anode conductors

· Usually replacement of the primary anode conductor wire or strips is necessitated as a result of mechanical damage rather than a failure of the anode conductor itself. Where replacement lengths of anode conductor are required to replace or bridge broken conductors they should be overlapped by a length of at least 500mm each side of the break. Each overlap is normally crimped or spot welded in 3 places at centres between 100mm and 150 mm. Each crimp connection is covered by suitable adhesive lined heat shrink sleeving.
Remote Monitoring and Control

It is a common practice to utilise remote electronic monitoring and control systems which are now available at an economic cost. Data acquired by an automated monitoring system, which is permanently installed on the structure, may be accessed remotely using an office-based computer. Remote monitoring offers significant benefits over manual monitoring including improved quality of data and reduced operating costs. In particular the reduced need for site access to the transformer-rectifier control cabinet allows a high elevation installation, which minimises the risk of vandalism or unauthorised interference.
Automated Monitoring

Introducing automated monitoring increases the opportunity to extend the scope of performance testing. For example, the full characteristic decay curve can be obtained for any time scale required, (4-24-72 hours) at all reference electrodes and can be carried out by the corrosion specialist from a remote office.

This superior data can be assessed and the cathodic protection system adjusted remotely, as necessary, from the specialist’s office.
System Requirements

There is currently no formally agreed document for the specification of remote monitoring and control systems although the draft European Standard pr EN 12961-2 does outline their requirements. The advice of the CP specialist should be sought to provide a detailed specification to ensure that the system fits the client’s and the structure’s requirements. As a general guidance the following should be complied with:

· The system should be capable of interrupting the power supply to each anode zone and acquiring instant-off data for all reference electrodes associated with the anode zone. Where a particular anode zone is likely to influence an adjacent anode zone, then the power supply to both zones must be simultaneously interrupted to acquire instant-off data.

· The system should be capable of monitoring the full potential depolarisation curve for each reference electrode and acquire data for up to 72 hours at operator specified intervals.

· The system should comprise modular data acquisition units suitable for permanent installation local to the structure and capable of independent operation.

· The data acquisition units should be capable of monitoring the required range of sensors at an appropriate level of accuracy.

· The system should enable the time and frequency of data acquisition to be operator specified and have sufficient temporary data storage capacity such that no data would be overwritten or lost.

· The system should have a degree of sophistication which will allow local area network communications to be established. Remote access from an office based computer to the LAN should be achieved via the telecommunications network using an industry standard modem.

· The system should be capable of fault diagnostics and reporting of equipment and communications failures.

· The system should enable the operator to set operational limits for all monitored sensors and be capable of alarm reporting of all monitored channels operating outside the set limits.

· The system should provide privileged access to all levels of system operation and allow access on entry of a valid operator name and associated password. The system should be capable of reporting unauthorised attempted access.

· The operation of the system should be “operator friendly”.

· The system software should provide graphical representation of data obtained locally or remotely at the time of retrieval and also of historical data.

· The system should be capable of storing acquired data as standardized ASCII text in an operator defined format to enable data transfer to a spreadsheet programme.

· The system should be capable of adjusting the dc constant current power output to the cathodic protection zones and to provide a limiting voltage or limiting current control.

Corrosion Mechanism

If mild steel is exposed to an aerated neutral aqueous solution, for example a dilute solution of sodium chloride in water, then corrosive attack will begin at defects in the oxide film on the steel. These defects may be present as a result of mechanical damage such as scratches, or may be due to natural discontinuities in the film, i.e. inclusions, grain boundaries or dislocation networks at the surface of the steel.

At each defect the steel is exposed to the solution (electrolyte) and an anodic reaction occurs, resulting in the formation of iron ions and free electrons. These electrons are then conducted through the oxide film to take part in a cathodic reaction at the surface of the film. This reaction requires the presence of dissolved oxygen in the electrolyte and results in the formation of hydroxyl ions.

The hydroxyl ions react with the ferrous ions produced by the anodic reaction to form ferrous hydroxide, which is then converted into a hydrated oxide called, ‘rust'. Gradually a scab of rust may form over the top of the pit, but this is too porous to completely block the anodic area. This allows the corrosion process to continue, resulting in deeper attack and widening of the anodic area as the surface oxide film breaks away.

If the pH of the solution in contact with the steel is low, for example a dilute acid, then the surface oxide film will be removed and the cathodic reaction will be different. Hydrogen gas will be liberated as gradual dissolution of the steel occurs. With oxidising acids, a number of alternate cathodic reactions may take place.

In all cases of corrosion the anodic reaction cannot proceed in isolation from the cathodic reaction and if either reaction can be limited or stopped then less or no corrosion will occur.

Mechanisms

Severe local attack such as pitting, (see figure 1) and crevice corrosion can be a particular problem in stainless steels and other alloys which depend on the presence of self healing (when oxygen is available), adherent and relatively defect-free oxide films for their resistance to corrosion.

Pitting

Pitting results from local breakdown of the barrier film which allows an anodic reaction to begin at point sites on the exposed metal. The cause of the point site may be local mechanical damage or chemical breakdown of the surface film, oxygen depletion beneath debris particles on the surface or chemical (galvanic effect) differences between second-phase particles or inclusions and the metal matrix.

Pitting is quite often self-accelerating due to local rises in acidity in the pits and is usually associated with the presence of certain ions, for example chloride and sulphide, in the corrosive environment. Such ions contribute to film breakdown and prevent film repair.
Stainless Steel Design

In stainless steels a minimum of 12% chromium is required in solid solution in the matrix to provide passivation by protective oxide film formation. Nickel additions (normally 6-10%), molybdenum and nitrogen are also used to improve general corrosion and pitting resistance. They also help to control matrix structure, for example to produce austenitic or duplex grades. In these steels, carbon content is kept as low as possible during alloy production. Subsequent processing, welding and heat treatment variables are carefully controlled to avoid the formation of Cr-rich carbide precipitates and other damaging second phases which can not only reduce toughness but also cause severe pitting and intergranular attack due to micro-galvanic effects.

A row of pits can form along deep scratches as the oxide film will not be impervious and the underlying metal will contain additional internal stress. Larger pits can form at dross and sand inclusions, highlighting the damaging effect of inadequate casting cleanliness. Casting defects such as shrinkage pores and inclusions can also result in severe local attack.

To minimise pitting, stainless steels are solution treated and quenched to dissolve second phase precipitates and to prevent their reformation on cooling. Due to the presence of chloride ions, conventional austenitic and duplex grades are prone to both pitting and crevice corrosion in seawaters but their resistance can be improved by additions of up to 6% Mo and 0.2-0.5% N.
Predicting Pitting Resistance

The relative behaviour of various grades can be compared by an empirical relationship for Pitting Resistance Equivalent (PREN), based upon laboratory corrosion tests in chloride containing solutions:



PREN = %Cr + 3.3%Mo X%N



where X = 16 for duplex and X = 30 for austenitic steels. The higher the PREN value the better the pitting resistance.

Hence super-duplex and super-austenitic grades give PREN values of 40-50, lean alloy duplex 27-30 and 18/8 (type 304) austenitic a value of about 20. For duplex structures, alloys are designed to produce ferrite and austenite phases with the same pitting resistance to avoid preferential attack of either phase.

Research into pitting and the growth of corrosion fatigue and stress corrosion cracks which are believed to originate at pits can now be aided by the use of special techniques which allow real-time mapping of local corrosion activity and the determination of localised corrosion rates. Such information is essential in the accurate prediction of safe working life.

Mechanism

In addition to the problems that can occur with stress corrosion cracking (SCC) due to the effects of static stress, in many situations, the applied stresses are cyclic due to mechanical or thermal effects. Under so called non corrosive conditions, cyclic or varying stress levels can result in fatigue damage at surfaces, leading to the growth of fatigue cracks and eventual failure.

Under corrosive conditions, fatigue cracks may be initiated, at corrosion pits for example, at a much earlier stage during service life and these cracks may well grow faster in the corrosive environment. The combined action of corrosion and fatigue will therefore be responsible for failure after a smaller number of stress cycles than would be expected in a non-corrosive situation.

In ferrous alloys, a fatigue (endurance) limit is obtained under non-corrosive fatigue conditions. At stress levels below this limit, fatigue failure is not expected. Corrosive conditions remove this limit, as shown schematically in Figure 1, giving the possibility of failure even at low levels of stress.

Corrosion fatigue tends to produce a number of growing cracks, rather than the more normal single crack in fatigue under conditions where corrosion has no influence. The corrosion fatigue cracks usually develop normal to the main tensile stress and do not branch, whereas SCC cracks are highly branched.

Corrosion fatigue fracture surfaces may or may not be coated with corrosion product depending on the relative effects of corrosion and stress. There will be more evidence of corrosion at lower stress levels or lower frequencies of stress cycling, because of the increased time of exposure. Unlike stress corrosion cracking, corrosion fatigue is a general problem and is not confined to a specific alloy environment combination.

Definition

Corrosion can be defined as the reaction of a material with its environment. The problem of corrosion arises in various environments ranging from urban and marine atmospheres to industrial chemical plant installations. It is a major factor governing the design and operation of plant and equipment as it reduces their useful life and can often result in unscheduled shutdowns or, in some cases, catastrophic failure. The control of corrosion presents a considerable challenge to engineers and, in spite of our best efforts, the annual costs of corrosion damage and corrosion related service failures run into many millions of pounds, estimated at about 4% of the GNP for an industrial country. However, there is scope to reduce this cost burden by making improvements in materials selection, methods of protection, design and in-service monitoring.

In aqueous environments, corrosion may occur as uniform (general) or non-uniform (local) attack. Uniform corrosion results in general wastage, is reasonably easy to inspect and to predict from weight loss experiments or electrochemical data. Local corrosion can take a number of various forms and is much less predictable. It can result in more serious damage to structures.
Passive Oxide Films

In order to understand both general and local forms of wet corrosion of metallic materials, the role of oxide films on their surfaces must be considered. All metals except gold will have a surface air-formed oxide film, the nature of the film depending on alloy composition and the conditions and temperature of its formation. Films which are strongly adherent and which do not contain imperfections are protective and can protect the underlying substrate against further dry oxidation or wet corrosive attack. Oxide films on the surfaces of metals are therefore seen to play a significant part in the mechanism of aqueous corrosion, as illustrated by the rusting of mild steel. Failures so caused are difficult to prevent due to the complex nature of the interaction of different corrosion mechanisms and residual and mechanical stresses in service. These mechanisms quite often give rise to non-uniform forms of corrosion that can result in severe local attack leading to failure.
Corrosion Mechanisms

Corrosion can proceed by several different mechanisms, including:

· Rusting of mild steel

· Differential aeration

· Pitting

· Galvanic attack

· Intergranular attack

· Leaching (selective corrosion)

· Corrosion and erosion

· Stress corrosion cracking (SCC)

· Corrosion fatigue

· Hydrogen damage
Design and Materials Selection

In short, corrosion damage takes many forms resulting from a variety of material/environment/stress interactions. In selecting materials to resist corrosion or taking corrosion protection measures, then total life cycle cost is probably the most significant factor. In this respect, the extra cost of inspection, maintenance and earlier replacement of cheaper, lower corrosion resistant materials have to be considered.

Materials have to be selected on the basis of their ability to resist specific corrosive environments and to withstand the levels of service stresses. The ease of fabricating the materials into the shapes required by the design is also an important consideration.

In the design process, potential corrosion problems may be prevented by avoiding:

· Shapes with crevices that might cause differential aeration

· Contact between incompatible materials which might give rise to galvanic attack

· Situations where small anodic sites are in contact with large cathodic areas