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How to Control Corrosion
ОглавлениеThere are many ways to organize and operate successful corrosion management systems, each of which is asset specific depending on factors such as Design, Stage in life cycle, Process conditions, and Operational history. The corrosion policy provides a structured framework for identification of risks associated with corrosion, and the development and operation of suitable risk control measures.
Corrosion is caused by a chemical reaction between the metal and gases in the surrounding environment. By taking measures to control the environment, these unwanted reactions can be minimized. Sacrificial coating involves coating the metal with an additional metal type that is more likely to oxidize, hence the term “sacrificial coating.” There are two main techniques for achieving sacrificial coating: cathodic protection and anodic protection. The most common example of cathodic protection is the coating of iron alloy steel with zinc, a process known as galvanizing. Anodic protection involves coating the iron alloy steel with a less active metal, such as tin. Tin will not corrode, so the steel will be protected as long as the tin coating is in place.
Another simple way to prevent corrosion is to use a corrosion‐resistant metal such as aluminum or stainless steel. Depending on the application, these metals can be used to reduce the need for additional corrosion protection. Though the application of a paint coating is a cost‐effective way of preventing corrosion. Paint coatings act as a barrier to prevent the transfer of electrochemical charge from the corrosive solution to the metal underneath. Corrosion inhibitors can be applied as a solution or as a protective coating using dispersion techniques. Corrosion inhibitors are commonly applied via a process known as passivation. Corrosion inhibitors are chemicals that react with the surface of the metal or the surrounding gases to suppress the electrochemical reactions leading to corrosion. They work by being applied to the surface of a metal where they form a protective film. Cathodic protection (CP) is by far the best way to stop corrosion on pipelines. It uses impressed currents from a fixed anode to interfere with the electrical circuit in the corrosion cell. It is 100% effective against most forms of external pipe corrosion.