Corrosion Rate of an Inorganic Zinc-Rich Primer with and without a Topcoat

Inorganic zinc-rich primers (IOZ) have been widely used over the last half-century as one of the best options for corrosion protection of carbon steel in atmospheric service environments where pH is relatively neutral. These primers have maintained a reputation for decades, supported by a quality track record in the lab with the most stringent qualification testing criteria established to date, as well as proven real-world performance in the field. Despite being one of the best options available, significant strides in advancing the overall performance of these primers have not been observed. Top-coating an inorganic zinc-rich primer may improve performance but also has the potential to result in problems unless further studies are conducted to ensure the topcoat works in favor of the combined coating system. This study monitors the corrosion rate and other electrochemical responses of an IOZ over time in ASTM(1) B1171 salt fog exposure to evaluate its behavior with and without an inorganic topcoat, as well as to standalone hot-dipped galvanized steel.