Paint, and other coatings act as barriers to corrosion whether crevice type (as at insertion points into a concrete capping), Splash zone rusting, or electrolytic cells in water. In the latter, salt water has a lower resistance to current than fresh water and therefore is a more severe corrosion environment.

Any coating can be let down by any ‘holiday’ in the film. Such holes can become highly preferential corrosion sites which may also give rise to corrosion creep under the coat. Therefore any coating system must be allied to a rigorous inspection system, particularly considering the likely occurrence of damage during construction (if the coat is factory applied). Any coating not factory applied is going to be suspect in a marine environment, especially if submerged. There are high specification paints formulated for underwater application, but these inevitably require highly experienced diving applicators. The advantage of a limpet dam, giving a ‘dry’ environment, for application and Quality Assurance (QA) is obvious, and the combination of coatings and plate repair may be beneficial.

Holidays in coatings generally become highly visible after a period of corrosion allowing a further visit for touch up. But this may be underwater!

Paint coating use can be economically linked to the use of cathodic protection.

Also see project datasheets.