Uniform Attack

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. 

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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. 

In certain alloys and under certain environmental conditions selective removal of one metal (the most electrochemically active) can occur resulting in either localised attack, with the consequent possibility of perforation (plug type), or in a more uniform attack (layer type) that results in a weakening of the strength of the component. Although the selective removal of metals such as Al, Fe, Co, Ni and Cr from their alloys is known, the most prevalent form of de-alloying is the selective removal of zinc from the brasses —a phenomenon that is known as dezincification. 

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. 

However, all existing security proofs are reduction proofs. To prove security against non-uniform attackers, one needs computational assumptions in the non-uniform model, too. Hence, all such theorems have a uniform and a non-uniform variant. As uniform reductions imply non-uniform reductions, but not vice versa, one has automatically proved both versions if one proves the uniform version [Pfit88, Gold91]. 

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],... 

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. 

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. 

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