Corrosion, combating

Drilling Muds in the Petroleum and Natural Gas Industry. Since 1941, chromium chemicals have been used in the drilling of wells to combat fatigue corrosion cracking of drill strings, with about one metric ton of sodium chromate being used aimuaHy for an average West Texas well. Other early uses were in gas-condensate wells in Louisiana and East Texas. 

Inhibitors The use of various substances or inhibitors as additives to corrosive environments to decrease corrosion of metals in the environment is an important means of combating corrosion. This is generally most attractive in closed or recirculating systems in which the annual cost of inhibitor is low. However, it has also proved to be economicaUv attrac tive for many once-through systems, such as those encountered in petroleum-processing operations. Inhibitors are effective as the result of their controlling influence on the cathode- or anode-area reactions. 

Coatings and Linings The use of nonmetaUic coatings and lining materials in combination with steel or other materials has and will continue to be an important type of construction for combating corrosion. 

When combating erosion-corrosion by changing tube metallurgy, caution must be exercised to ensure appropriate tube and baffle spacing so that vibration-associated cracking problems are not introduced. 

The most successful way of combating exhaust-system corrosion is, in fact, stainless steel. This is a good example of how - just as with dry oxidation - the addition of foreign atoms to a metal can produce stable oxide films that act as barriers to corrosion. In the case of stainless steel, Cr is dissolved in the steel in solid solution, and Cr203 forms on the surface of the steel to act as a corrosion barrier. 

Primers are required to be resistant to all of the same fluids and environments as the adhesive, and are in addition expected to be compatible with secondary finishes such as corrosion and fluid resistant primers applied to cured bond assemblies. The most commonly used primers for 250°F cured epoxy adhesives also have active corrosion inhibitors themselves to combat corrosion at bondlines. This last requirement is somewhat dated, evolving from the severe corrosion and delamination problems experienced before U.S. airframe manufacturers adopted durable surface treatments. 

The best way to combat corrosion is to maintain an effective corrosionmonitoring program to supplement good preventative measures. It is also very important to keep complete records of monitoring programs, control programs and failures that occur. The importance of well-qualified responsible personnel cannot be overemphasized as effective corrosion control depends on their efforts [201,204,205]. 

Bush, H. E., Treatment of drilling fluids to combat corrosion, SPE No. 5123, SPE 49th Annual Fall Meeting, Houston, October 1974,... 

Brigham, R. J. andTozer,E. W., Temperatureas a Pitting Criterion , Corrosion, 29,33(1973) Bruce, S., Specialist Steels Combat Corrosion by Chloride-containing Cooling Water , Process Eng., 88 (1973) C.A., 80, 6176k... 

In overlay bearings operating above about 140°C, the tin or indium in the overlay diffuses towards, and alloys with, the underlying copper, depleting the overlay and reducing its resistance to corrosion. This depletion by diffusion can be combatted by the use of a diffusion barrier or dam , e.g. a nickel-rich layer between the bearing alloy and, the overlay . 

The spraying process provides a method of treating steel with coatings of zinc or aluminium, which can afterwards be painted. A combination of such a metallic primer and a good peunt system is the most effective means of combatting corrosion of constructional steelwork at a reasonable cost that is yet known. 

A recent application of this type of fluid is assistance in the removal of ingested salt spray from jet aircraft compressors and the neutralisation of corrosive effects. Other types of water-displacing fluids are claimed to have fingerprint neutralising properties or to be suitable for use on electrical equipment. Some oil-type materials serve temporarily as engine lubricants and contain suitable inhibitors to combat the corrosive products of combustion encountered in gasoline engines. 

Ammonium salts of alkenyl succinic half-amides have teen described for use as corrosion inhibitors in oil and gas production technology to combat corrosion by media containing CO2, H2S, and elemental sulfur [1366]. The inhibitor composition may contain a dispersing agent, such as a low molecular weight or polymeric anionic surfactant like an alkylsulfonic acid or an alkyl-aryl sulfonic acid. 

Compounds of magnesium can be added to fuel containing vanadium to help combat its corrosive effects. Typical addition rates range from 2 1 Mg V at a 1200°F (648.9°C) operating temperature and 3 1 Mg/V at a 1,500°F (815.5°C) operating temperature. However, the total ash content must still be monitored. 

Engine lubricant formulators are aware of the problems associated with fuel sulfur and develop products to help combat its corrosive effect. Lubricants containing overbased calcium sulfonates and phenates are utilized to chemically neutralize the acids which form as a result of burning fuel sulfur. These oils can be effective at preventing the corrosive effects of fuel sulfur. However, the oils must be frequently changed to ensure that the acid-neutralizing effect is maintained. 

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