Using DC electrochemical techniques to assess the relative corrosiveness of water-based coatings and their ingredients

It has been common to assess corrosion inhibitors by ranking their relative corrosion currents at some arbitrary potential above the open circuit potential via DC potentiodynamic anodic scans. Groseclose et al.1 demonstrated that when bare steel panels are subjected to such scans, the difference in mV between the open circuit potential and breakdown potential is a sensitive measure of the panels’ tendency to corrode once coated and exposed to a corrosive environment. The present authors show that a combination of the two DC electrochemical techniques can be used to assess the relative corrosion (or inhibition) contribution of various ingredients in water-based coatings, and that those results translate into the same order of behavior when coatings utilizing those ingredients were applied to steel and tested in a corrosive environment. This technique is also shown to be capable of ranking finished liquid paints for their subsequent corrosion resistance as dried coatings on steel, and verifying the batch consistency of liquid paints in production.