Corrosion causes

Wash regularly the tower structure, in the absence of rains sufficient to wash the tower free of salt. 

American consumers, businesses, and government organizations own more than 200 million registered vehicles. Assuming a value of 5000 for each vehicle allows an estimate that Americans have more than 1 trillion invested in their motor vehicles, making automobiles one of the largest investments collectively among Americans. 

Several factors lead to various types of corrosion in motor vehicles, specifically the design process, the manufacturing process, and operating conditions. 

The corrosivity of the local environment will strongly affect the corrosion performance of the vehicle (19,20). In locations where corrosive environments are possible because of acid rain, deicing salts, or marine environments, personal driving habits and diligent maintenance of the vehicle, such as regular washing and replacement of fluids, can have a significant effect on the reduction of corrosion. 

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Localized erosion-corrosion caused by turbulence or impinging flow at certain points of the surface. In the majority of cases of impingement attack, a geometrical feature of the system results in turbulence at one or more parts of the surface. 

Although ceramic electrodes have received much attention (101), they have not been successful in channels operating with slag-laden flows, because of excessive electrochemical corrosion caused by the slag. Only weU-cooled metallic elements have been used successfully in slagging environments. 

The main cause of anode wear is electrochemical oxidation or sulfur attack of anodic surfaces. As copper is not sufficiently resistant to this type of attack, thin caps of oxidation and sulfur-resistant material, such as platinum, are bra2ed to the surface, as shown in Eigure 15a. The thick platinum reinforcement at the upstream corner protects against excessive erosion where Hall effect-induced current concentrations occur, and the interelectrode cap protects the upstream edge from anodic corrosion caused by interelectrode current leakage. The tungsten undedayment protects the copper substrate in case the platinum cladding fails. 

Cooling System Corrosion Corrosion can be defined as the destmction of a metal by chemical or electrochemical reaction with its environment. In cooling systems, corrosion causes two basic problems. The first and most obvious is the failure of equipment with the resultant cost of replacement and plant downtime. The second is decreased plant efficiency to loss of heat transfer, the result of heat exchanger fouling caused by the accumulation of corrosion products. 

Some units have been built and successbilly operated with simple slot-type distributors made of heat-resistant steel. This requires a heat-resistant plenum chamber but eliminates the frequently encountered problem of corrosion caused by condensation of acids and water vapor on the cold metal of the distributor. 

Ferrous sulfate was added to the condenser in hopes of retarding attack. A thick, tan deposit layer rapidly formed on tubes near inlets (Fig. 4.24). Corrosion continued unabated. Underdeposit corrosion caused localized areas of metal loss (Fig. 4.25). Corrosion product mounds contained up to 10% chloride. 

Figure 5.4 EfTect of temperature on corrosion of iron in water containing dissolved oxygen. (Courtesy of McGraw-Hill Inc., Corrosion, Causes and Prevention, by F. Speller, p. 168, McGraw-Hill, 1951)...

Passive corrosion caused by chemically inert substances is the same whether the substance is living or dead. The substance acts as an occluding medium, changes heat conduction, and/or influences flow. Concentration cell corrosion, increased corrosion reaction kinetics, and erosion-corrosion can he caused by biological masses whose metabolic processes do not materially influence corrosion processes. Among these masses are slime layers. 

Reducing pH usually has a beneficial effect on corrosion caused by alkaline substances. However, this seemingly obvious solution has a number of drawbacks. Chemical treatment programs work most effectively in certain pH ranges. Decidedly acidic waters can cause corrosion problems as bad or worse, albeit different, than those caused by alkaline waters. Finally, if concentration mechanisms such as evaporation or condensation are present, merely decreasing pH may prove ineffective in controlling attack. 

Microstructural examinations revealed V-shaped openings along the tube seam, some extending into as much as 50% of the tube wall thickness. The incompletely closed seam provided a crevice in which differential concentration cells developed (see Chap. 2, Crevice Corrosion ). The resulting localized corrosion caused the observed pits. 

Graphitic corrosion is a slow corrosion process, typically requiring many years to effect significant damage. Complete penetration of thick cross sections has, however, occurred in as little as 2 years in adverse environments. On the other hand, cast iron components can be found in use in Europe after 160 years of service. Although graphitic corrosion causes a substantial reduction in mechanical strength, it is well known that corroded cast iron, when sufficiently supported, may remain serviceable when internal pressure is low and shock loads are not applied. 

Speller, F. N., Corrosion/Causes and Prevention, McGraw-Hill, Inc., New York, 1951. 

Cooling water system corrosion causes immediate and delayed problems. Difficulties spread from a failure like ripples from a pebble thrown into a pool. A single failure may force an unscheduled outage, redirect worker efforts, contaminate product, compromise safety, increase equipment expense, violate pollution regulations, and decrease productivity. 

Fig. 12-1 Danger of corrosion caused by cell formation with steel-reinforced structures and of the pipe/soil potential.

Corrosion is described as hot corrosion and sulfidation processes. Hot corrosion is an accelerated oxidation of alloys caused by the deposition of Na2S04. Oxidation results from the ingestion of salts in the engine and sulfur from the combustion of fuel. Sulfidation corrosion is considered a form of hot corrosion in which the residue that contains alkaline sulfates. Corrosion causes deterioration of blade materials and reduces component life. 

Impingement is corrosion caused by aerated water streams constricting metal surfaces. It is similar to erosion corrosion in which air bubbles take the place of particles. The pits formed by impingement attack have a characteristic tear drop shape. 

Corrosion-caused failures occur at a rate of two per year. 

Carbon dioxide dissolves in water to form a weak acid (carbonic acid), which reduces the pH of the solution and, consequently, increases its corrosivity. Corrosion caused by carbon dioxide is generally referred to as sweet corrosion, and results in pitting. The mechanism of carbon dioxide corrosion is as follows [197,198] ... 

A higher glycol yield (approximately 94%) than from the ethylene oxide process is anticipated. However, there are certain problems inherent in the Oxirane process such as corrosion caused hy acetic acid and the incomplete hydrolysis of the acetates. Also, the separation of the glycol from unhydrolyzed monoacetate is hard to accomplish. 

Robinson, F. P. A., Pitting Corrosion Cause, Effect, Detection and Prevention , Corrosion Technol., 7, 237, 266 (1960)... 

LaQue, F. L., Marine Corrosion, Causes and Prevention, John Wiley Sons, New York (1975) Schumacher, M., Sea Water Corrosion Handbook, Noyes Data Corp., Park Ridge, N.J. (1979) Gilbert, P. T., Mater. Performance, 21 (2), 47 (1982)... 

Henthorne, M., Intergranular Corrosion of Iron and Nickel Base Alloys, Localised Corrosion-Cause of Metal Failure, ASTM STP 516, ASTM, 66 (1972)... 

In nearly all known cases of stray-current corrosion the damage is caused by direct currents, but leakages of alternating currents at industrial frequencies have been suspected of causing corrosion of buried metallic structures. The mechanism of corrosion caused by a.c. is not clearly understood and fresh studies are being made. However, the corrosion caused is much less severe than with stray d.c. and experiments indicate that stray a.c. at 50Hz will produce less than 1 % of the corrosion caused on most buried metals by an equivalent d.c. 

The amount of corrosion damage resulting from the operation of d.c. railways is generally less than the corrosion caused by street tramway systems since the railway track insulation is better, the frequency of service is less, and pipes and cables are usually buried further from the running rails. 

Test method for assessing galvanic corrosion caused by the atmosphere... 

Ruseska, I., Biocide Testing Against Corrosion-Causing Oil Field Bacteria Helps Control Plugging , Oil and Gas J., 253-264, 8 March (1982)... 

Stray-current Corrosion corrosion caused by stray currents flowing from another source of e.m.f. (usually d.c.). 

Frozen Foods. Corrosion caused by the reaction of foods with aluminum containers is unusual if the products are handled and stored at 0°F or lower. However, the inevitable bad handling of frozen foods during commercial distribution causes undesirable thawing. In this condition, not only does the food deteriorate, but it can also attack the container. Such unwanted reactions can be effectively controlled by using coated aluminum containers. Since aluminum is highly compatible with frozen fruits and citrus juices, it has been used extensively as a liner for fiberboard composite cans, as complete aluminum cans, or as ends in combination with steel can bodies in the frozen food industry. 

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