Protective Coatings Against Surface Corrosion

June 16, 2010

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The application of corrosion resistant coatings is one of the methods used to combat the electrochemical process of corrosion. Without these coatings, substrates like steel corrode easily. When the steel material fall to corrosion, its service life is shortened and can even result to severe structural failure.

When applied, certain corrosion resistant coatings undergo a curing process wherein the accompanying solvent completely evaporates. The resins of these coatings – vinyl, acrylics, bitumen and chlorinated rubbers – are left in original form, adherent to the surface after application.

Another type of protective coatings cures with the help of an irreversible polymerization process that completely changes the chemical composition of the original resin. Polymerization can be induced with the aid of oxygen, such as in the case of alkyds and certain thin-film oils. Epoxy and polyurethane corrosion resistant coatings, on the other hand, undergo a chemically-induced polymerization process.

Corrosion resistant coatings based on silicone have heat-induced polymers capable of withstanding extremely high temperatures. They are often used for corrosion control in boilers and furnaces.

Some protective coatings polymerize through hydrolysis. Moisture-cured polyurethanes are a good example of these. When applied, a protective film is created through the reaction with air-borne moisture. The same reaction is present in inorganic zinc coatings that are dispersed as zinc metal in powder form. When the coatings react with water in the air, they change to form a strong barrier. The zinc particles act as sacrificial materials to protect steel structures like bridges from corrosive agents.

The choice of corrosion resistant coatings depends on their intended use and application. Most corrosion control projects also consider the cost of paints in the selection process.

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