Anti-corrosion surface treatment of fasteners


In industrial process facilities, corrosion is the biggest single cause of plant and equipment breakdown, including machinery, vessels, structures, supports and pipelines. Although atmospheric corrosion in the form of air (oxygen), and water (moisture, humidity, vapour, etc.) is the main culprit, environmental factors including high temperatures and pressures as well as harsh substances, chemicals and gasses can also accelerate the corrosion of carbon steel and other metals.

Beyond marine environments exposed to salt spray or compounds that cause corrosion, common gaseous industrial air pollutants, such as sulphur dioxide, ozone, and nitrogen dioxide, can be corrosion inducing. So can exposure to industrial chemicals such as chlorides, acetic acid and formaldehyde. “There is a huge need for an anti-corrosion coating that can go on in areas where conventional coatings tend to fail,” says Joey Taylor, President of IPI, a US-based paint/coating contractor for commercial and industrial construction. “On certain projects, chlorides need to be removed to meet peak performance. But in most cases, this can be cost prohibitive.”

Fortunately, for industrial facilities with assets prone to environmental corrosion, a new category of tough, chemically bonded phosphate ceramic (CBPC) coatings is helping to stop corrosion, ease application and reduce production downtime.

When aluminium is recycled, it is melted to separate the pure metal from the impurities. The process creates a waste product called salt cake, which contains compounds that can promote corrosion. As a result, typical barrier-type anti-corrosion coatings, such as polymer paints, can fail prematurely. This is particularly true when the paint is scratched, chipped or breached and corrosion promoters enter the gap between the substrate and coating. Then the coating can act like a greenhouse – trapping the corrosion promoters – that allows the corrosion to spread under the coating.