Corrosion uniform attack

To summarise, unexpected corrosion failures are much more likely to occur by localised attack than by uniform attack (which can easily be detected) and although corrosion handbooks are useful for making initial choices of materials for applications where corrosion is important, critical components must be checked for life-to-fracture in closely controlled experiments resembling the actual environment as nearly as possible. 

These considerations lead to the conclusion that the relationship between corrosion and deterioration of properties of a metal is highly complex, and involves a consideration of a variety of factors such as the rate and form of corrosion and the specific function of the metal concerned certain forms of corrosion such as uniform attack can be tolerated, whereas others such as pitting and stress corrosion cracking that ultimately lead to complete loss of function, cannot. 

Uniform attack on a metal results in uniform corrosion. This is exploited in the processing and finishing of metals (Chapter 15). However, metallic structures are rarely homogeneous and surfaces are rough corrosion occurs, preferentially within fissures in the surface (crevice corrosion), making corrosion faster. 

In reality, the identification of one or more forms of corrosion requires visual observation, nondestructive inspection methods, optical microscopic examination, and sometimes electron scanning microscopy, etc. The first study of the corrosion appearance of a case should divide corrosion into uniform and localized corrosion. Localized corrosion can be further identified as macroscopic or microscopic local corrosion. Microscopic attack refers to a minute amount of dissolved metal, accompanied by considerable damage, before the phenomenon becomes visible to the naked eye. 

For example, the acid will uniformly corrode a piece of mild steel sheet immersed in dilute sulfuric acid. Corrosion by uniform attack accounts for the greatest loss in practice. The incidence of this kind of corrosion can easily be detected and remedial measures taken. 

Electrochemical corrosion is important to the stability and longevity of implants. Evidence suggests that uniform attack and crevice and pitting corrosion are the most important degradation modes with multipart orthopedic devices (17). Corrosion of devices with blood contact is more complex, due to the oxygenated flowing electrolyte. The cost of this corrosion has not been estimated, but it could be substantially greater than the battery market because the latter is a small fraction of the total cost of the device and associated medical operations. 

Single-component corrosion types, important for heat exchanger design and operation, are as follows (1) uniform attack corrosion, (2) galvanic corrosion, (3) pitting corrosion, (4) stress corrosion cracking, (5) erosion corrosion, (6) deposit corrosion, and (7) selective leaching [153],... 

CORROSION, UNIFORM - The simplest form of corrosion. It attacks all surfaces exposed to a corrodent. 

Several examples of the results of crevice corrosion are shown in Figs. 3 to 6. The similarities in topography amongst the examples include the accelerated attack of the substrate under the crevice former and the virtual absence of attack on the fully exposed surface. The accelerated attack within the crevice usually appears as uniform corrosion or pitting. In some cases, it is thought that the attack starts as metastable pits that coalesce into a more uniform attack. 

Mortar Uniform corrosion localized attack Copper release Perforation of pipe and leakage... 

In addition to ductile iron and PVC, copper and lead are used in pipes, and brass in fixtures and connections. Lead is released because of uniform corrosion. Copper is also released because of uniform corrosion, localized-attack cold water pitting, hot water pitting, MIC, corrosion fatigue, and erosion-corrosion. Lead pipes and lead-tin solder exhibit uniform corrosion. Brass corrosion includes erosion-corrosion, impingement corrosion, dezincification, and SCC. The direct health impacts are because of increased copper, lead, and zinc concentrations in the drinking water. Mechanical problems because of corrosion include leaks from perforated pipes, rupture of pipes, and the loss of water pressure because of blockage of pipes by corrosion products. 

Corrosion within pump and piping systems is another problem, and general uniform attack is common. Pitting, crevice corrosion, intergranular corrosion, dealloying, galvanic corrosion, and cavitation corrosion are also possible depending on the environment. 

Uniform attack over large areas of a surface is the most common form of corrosion. Corrosion of metals can either be uniform or localized. This attack can be either wet or dry, or chemical or electrochemical. Unexpected failures from uniform corrosion can be avoided by periodic and regular inspection. 

This form of corrosion accounts for most of the destruction of metals on a tonnage basis. From a technical standpoint, however, uniform attack causes the least concern, largely because service life can often be quite accurately estimated on the basis of relatively simple corrosion tests. In contrast, a localized form of corrosion often results in an unexpected failure because it is difficult to predict in advance and to observe during inspection. 

General Corrosion, or Uniform Attack. This type of corrosion includes the commonly recognized rusting of iron or tarnishing of silver. Fogging of nickel and high-temperature oxidation of metals are also examples of this type. 

Uniform attack or general corrosion is the most common form of corrosion. It is normally characterized by a chemical or electrochemical reaction that proceeds uniformly over the entire exposed surface or a very large area. This mechanism has not been a significant concern with spent nuclear fuel in wet... 

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