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Concentration Cell Corrosion Crevice

The classification given in Table 1.2 is based on the various forms that corrosion may take, but the terminology used in describing corrosion phenomena frequently places emphasis on the environment or cause of attack rather than the form of attack. Thus the broad classification of corrosion reactions into wet or dry is now generally accepted, and the nature of the process is frequently made more specific by the use of an adjective that indicates type or environment, e.g. concentration—cell corrosion, crevice corrosion, bimetallic corrosion and atmospheric corrosion. [Pg.14]

Concentration cell corrosion (crevice corrosion, under-deposit corrosion, tuberculation, pitting corrosion)... [Pg.562]

The three major forms of concentration cell corrosion are crevice corrosion, tuberculation, and underdeposit attack. Each form of corrosion is common in cooling systems. Many corrosion-related problems in the cooling water environment are caused by these three forms of wastage. The next three chapters—Chap. 2, Crevice Corrosion, Chap. 3, Tuberculation, and Chap. 4, Underdeposit Corrosion — will discuss cooling water system corrosion problems. [Pg.9]

Finally, pitting may be viewed as a special form of concentration cell corrosion. Most alloys that are susceptible to crevice corrosion also pit. However, many metals may pit but not show crevice attack. Further, although sharing many common features with concentration cell corrosion, pitting is sufficiently different to warrant a separate categorization. [Pg.11]

Concentration cell corrosion occurs in an environment in which an electrochemical cell is affected by a difference in concentrations in the aqueous medium. The most common form is crevice corrosion. If an oxygen concentration gradient exists (usually at gaskets and lap joints), crevice corrosion often occurs. Larger concentration gradients cause increased corrosion (due to the larger electrical potentials present). [Pg.14]

Localized, concentration-cell corrosion (differential aeration corrosion), occurring as Tuberculation corrosion Crevice corrosion Under-deposit corrosion Pitting corrosion All forms of localized, concentration-cell corrosion are indirect attack type corrosion mechanisms. They result in severe metal wastage and can also induce other corrosion mechanisms, e.g. Stress corrosion Corrosion fatigue... [Pg.270]

MIC almost always acts in concert with other corrosion mechanisms and may, at times, appear to be crevice corrosion, underdeposit acid attack, oxygen-concentration cell corrosion, ion-concentration cell corrosion, and CO2... [Pg.80]

Sulfates are causative agents (along with oxygen, hydrogen, etc.) of the various types of concentration cell corrosion that result in pits, crevice attack, or tuberculation. [Pg.92]

Crevice corrosion, under-deposit corrosion, and tuberculation are all forms of concentration cell corrosion, and all involve oxygen to a greater or lesser extent. [Pg.97]

Crevice corrosion, and concentration cell corrosion, susceptibility can be measured directly, by exposing test specimens to the environment. ASTM F 746, G 48, and G 78 can be used for evaluating these forms of corrosion. These methods were designed to measure crevice corrosion in severe electrolytes such as salt solutions, but can be modified for freshwaters. [Pg.384]

Potential differences leading to galvanic-type cells can also be set up on a single metal by differences in temperature, velocity, or concentration (see subsection Crevice Corrosion ). [Pg.2418]

Local variations in temperature and crevices that permit the accumulation of corrosion products are capable of allowing the formation of concentration cells, with the result of accelerated local corrosion. [Pg.2428]

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. [Pg.319]

Chemical removal of deposits and corrosion products revealed the appearance of the groove (Fig. 14.5). The crevice formed by the incompletely fused weld seam fostered the establishment of differential concentration cells (see Chap. 2). This resulted in localized corrosion and eventual perforation through the greatly thinned tube wall at the bottom of the crevice. The tubercle, which is composed of corrosion products, is a simple result of the corrosion process occurring locally within the crevice. [Pg.321]

Figure 53.4 Crevice corrosion driven by (a) a differential aeration cell and (b) a differential metal ion concentration cell... Figure 53.4 Crevice corrosion driven by (a) a differential aeration cell and (b) a differential metal ion concentration cell...
Crevice corrosion of copper alloys is similar in principle to that of stainless steels, but a differential metal ion concentration cell (Figure 53.4(b)) is set up in place of the differential oxygen concentration cell. The copper in the crevice is corroded, forming Cu ions. These diffuse out of the crevice, to maintain overall electrical neutrality, and are oxidized to Cu ions. These are strongly oxidizing and constitute the cathodic agent, being reduced to Cu ions at the cathodic site outside the crevice. Acidification of the crevice solution does not occur in this system. [Pg.893]

In addition to the basic corrosion mechanism of attack by acetic acid, it is well established that differential oxygen concentration cells are set up along metals embedded in wood. The gap between a nail and the wood into which it is embedded resembles the ideal crevice or deep, narrow pit. It is expected, therefore, that the cathodic reaction (oxygen reduction) should take place on the exposed head and that metal dissolution should occur on the shank in the wood. [Pg.970]

Under-Deposit Corrosion In the same way that oxygen becomes depleted in a crevice, and a differential-oxygen concentration cell is established, leading to localized corrosion of the oxygen-starved anodic area, so the same phenomenon readily occurs in dirty boilers under deposits, sludge, and other foulants. [Pg.248]

Figure 6.20 Two types of crevice corrosion oxygen concentration cell and metal ion concentration cell774... Figure 6.20 Two types of crevice corrosion oxygen concentration cell and metal ion concentration cell774...
Production of differential aeration cell. A scatter of individual barnacles on a stainless steel surface creates oxygen concentration cells. The formation of biofilm generates several critical conditions for corrosion initiation. Uncovered areas will have free access to oxygen and act as cathodes, while the covered zones act as anodes. Underdeposit corrosion (crevice corrosion) or pitting can occur. Depending on the oxidizing capacity of the bacteria and the chloride ion concentration, the corrosion rate can be accelerated. However, the presence of a biofilm does not necessarily mean that there will always be a significant effect on corrosion. (Dexter)5... [Pg.388]

In discussing environment, we can look at its effect on a macro scale, e.g. in the atmosphere, in the ocean, etc. and also examine effects on a micro scale, i.e. what is happening on the metal surface or over short distances. Due to the great variety of environments in which metals are put to use, the range of corrosion problems are equally numerous. Often, similar types of corrosion occur in many environments and may stem from similar mechanisms these have been given specific names which indicate how the corrosion has occurred. For example, under-deposit corrosion and crevice corrosion are related, both being due to oxygen concentration cells. [Pg.241]


See other pages where Concentration Cell Corrosion Crevice is mentioned: [Pg.5]    [Pg.5]    [Pg.297]    [Pg.395]    [Pg.165]    [Pg.170]    [Pg.7]    [Pg.2683]    [Pg.2660]    [Pg.229]    [Pg.229]    [Pg.384]    [Pg.198]    [Pg.701]    [Pg.67]    [Pg.111]    [Pg.1294]    [Pg.1000]    [Pg.247]    [Pg.98]    [Pg.98]    [Pg.360]    [Pg.361]   


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