Corrosion Protection of Aluminum Alloys by Vanadate Pigments in Epoxy Primers

Abstract : ONGOING WORK (1) Artificial scratch cell: The artificial scratch cell setup is being used to further evaluate whether meta-vanadates released from the coating could protect bare Al surfaces. (2) Coating degradation: A detailed EIS analysis on coatings with and without intentional defects is also being conducted. Results thus far have shown lower break point frequencies and larger Z(10mHz) values when vanadates were added to the primer in line with the results of ASTM B117 testing. (3) Inhibition studies on aeronautical magnesium alloys by meta-vanadates are being conducted. CONCLUSIONS: Adding NaVO3 to plain epoxy primers greatly improved coating performance. In the presence of meta-vanadates no blistering or corrosion products were found after 2 weeks of exposure to the salt fog chamber. Vanadium was found along the scribe, likely suggesting diffusion of the inhibitor from the coating to the bare Al surface. The slightly alkaline environment of the chamber could reduce the risk of deca-vanadate precipitation.