Pitting mitigation

Since pitting is an electrochemical process, it can be stopped by cathodic protection. It can also be prevented by the use of inhibitors to alter the electrode reactions of the local cell and remove their driving force. In some cases, agitation of the environment will prevent environmental differences from developing and will prevent pitting that otherwise would occur. 

Penetration by pitting is often prevented by coating the surface of a metal with a sacrificial layer of another alloy, such as zinc on steel or Alclad on aluminum, or by appl5dng protective coatings. A zinc-rich paint is sacrificially active and will prevent the pitting of either steel or aluminum. 

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Controversy concerning the interpretation of cyclic polarization curves has raged for many years. Of particular interest is which (if either) of the two potentials can be used for material selection and mitigation strategy decisions. The classic interpretation is that a material s potential must exceed Ehl[ in order to initiate pits, but if flaws were introduced into the surface in any way, they could propagate at all potentials above Ew. Thus Eq, could be used in design as a protection potential. 

Odour mitigation in the food industry, sewage treatment plants, animal carcass rendering plants, composting plants, waste disposal plants and refuse pits. 

Design-to-prevent is a useful approach to avoid pitting and crevice corrosion. Some examples of surface treatments and coatings to mitigate pitting and crevice corrosion are the following ... 

Aluminum alloys are susceptible to underdeposit corrosion. Stainless steels are also susceptible to underdeposit corrosion as well as deep pitting. Anodic, cathodic, and filming inhibitors are used to mitigate corrosion (40). 

External corrosion of tanker tmcks and railcar-mounted tanks is a problem. Both general and pitting corrosion from the atmosphere and splash water from the roadway or rail bed can affect the tank s structural integrity. This can be a serious problem in locations where chloride sources are present such as road salt or airborne marine atmosphere and airborne industrial pollution. The common mitigation method involves painting of the tanks. 

Note that even risks which are considered to be low and might otherwise be taken as acceptable by default still require mitigation if this is at all possible. The seemingly bottomless pit of risk mitigation can be qualified by a risk benefit analysis, i.e. the ability to justify the risk against the product s benefits rather than the cost or effort of further risk reduction. The risk benefit analysis also needs to include the benefits of using an alternative product. 

When the phenomenon is known only poorly, the collected data may contain some degree of randomness or even reflect beliefs and bias on the part of the collector. To mitigate this problem, analysts may rely on probability, which relates statistical concepts to stochastic variables by mean of large data sets. An example of the use of one statistical and probabilistic method is the use of extreme value distributions applied to cumulative distribution functions to analyze pitting corrosion as performed by Macdonald and colleagues and shown in Figure 3.5. ... 

The corrosion-like electrochemical process of material removal refers to spatially uniform general corrosion of the metal surface. However, the wet CMP environment can also support certain other types of undesirable electrochemical corrosions, such as localized pitting, and bimetallic/galvanic decomposition that contribute to surface defects. The considerations for mitigating these defects constitute a major aspect of slurry (additive) selection, which in turn can be facilitated by the use of electrochemical techniques. 

Li-K and Li-Na carbonate melts had different corrosirMi behaviors with 316 L. These melts showed insignificant corrosirMi at 650PC but severe pit corrosion was observed only in the Li-Na melt under the present O2 and CO2 condition at around 550 C [10, 11]. Mitsubishi Electric Co. reported that an inert gas condition in the temperature range could prevent severe corrosion [10]. IHl in Japan also reported that the corrosion is mitigated by pre-oxidation of the surface by steam [11]. 

Barriers can be designed to be passive or active in nature. Passive safety barriers provide a natural fixed roadblock, such as a tank pit or a firewall. Active barriers provide a response to certain states or conditions they involve a sequence of detection, diagnosis, and action (also referred to as detect-diagnose-deliect). Both physical and nonphysical barriers are utilized and apphed in hazard control and risk mitigation. Anything used to control. 

Pitting and intergranular corrosion can be mitigated by cathodic protection and Inhibitor release... 

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