Use of electrochemical noise method to investigate the anti-corrosive properties of a set of compliant coatings

This particular study has the aim of developing a new set of reduced VOC (also known as compliant) coatings. The reasoning for this is linked with the mass reduction scheme (MRS) and the requirement for environmentally friendly coatings. To this end a comparison needs to be made between these products and the higher solvent products which it is hoped that they will replace. Accelerated tests are required to get results in reasonably short times. Previous work has established the electrochemical noise method (ENM) as a useful technique for investigating the corrosion resistance of intact organic coatings on steel substrates. To date the most useful parameter obtained has been resistance noise (Rn) and results have shown that coatings that effectively protect the metal substrate demonstrate considerably higher Rn values and these remain high with time. In this work ENM has been used to monitor intact coatings under immersion conditions. Results will be given and compared with standard “salt spray” testing. The immersion test has also had a temperature cycle incorporated and this latter modification makes it effective at separating coatings within an even shorter time. The results so far look very promising and this test regime is helping the company to formulate the lower solvent replacements to be as effective from the anti-corrosion angle as the coatings which they will replace.