Blistering

Blistering of coating systems has multiple causes. One example is solvent entrapment, which may have resulted from excessive film thicknesses, too much thinners added to the product, using the wrong thinner or a combination of factors. DCC has the ability to test the presence and types of solvent in blistered coating films using GLC-analysis.

When blistering occurs in immersion conditions and under cathodic protection so called “cathodic disbondment” may have occurred. The coating film is pushed off the substrate due to the formation of hydroxyl and hydrogen gas. These gasses are formed by the currents that have been imposed on the substrate and the presence of water at the interface of coating and substrate.   By measuring the pH value of the liquid inside the blister, the possible role of an impressed current system in the formation of blistering can be determined.