Protecting fasteners in highly corrosive environments

Paul Boughton

DuPont has developed a new water-based, low-VOC coating solution based on Teflon PTFE for fasteners in highly corrosive environments. This one-coat system is particularly suitable for applications requiring very high corrosion resistance, dry lubrication and anti-seize properties to prevent galling.

Typical applications are screws and bolts made from substrates such as carbon steel, special steel and aluminium used in offshore oil and gas extraction, the chemicals industry or in water treatment plants.

Results from a salt spray test according to ASTM B117 carried by an independent laboratory have confirmed that screws treated with this new coating solution have outstanding corrosion resistance even without surface pretreatment.

Corrosion resistance can be still further improved by using suitable primers or substrate pretreatments. For instance, carbon steel bolts with a zinc base coat of just 7.5µm and a Teflon anti-corrosion coating of just 20 to 30µm have less than 10% red rust even after 3,000 hours' exposure.

The new coating system is free of heavy metals, its VOC content is below 0.36g/l and no special solvents are needed for clean-up and thinning, just water. Thanks to the low coefficient of friction of PTFE less torque is required for tightening.

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