The Electrochemical Behavior of As-Prepared Aluminum Alloy A360 Produced by Selective Laser Melting Fabrication with and without a Trivalent Chromium Process Conversion Coating


 We report herein on the electrochemical behavior and corrosion resistance of as-prepared aluminum alloy, A360 (AlSi10Mg), prepared by additive manufacturing (AM), with and without a trivalent chromium process (TCP) conversion coating. Selective laser melting (SLM) was the 3D printing process used for the alloy build. The coating system performance, in terms of corrosion suppression, was assessed through electrochemical measurements and accelerated degradation testing, specifically a 14-day continuous neutral salt-spray (ASTM B117) exposure. The results indicate that a TCP conversion coating can be formed optimally by solution processing (degreasing and deoxidation) the alloy (x-z plane perpendicular to the build direction) with its native surface roughness (as-prepared) followed by immersion for 15 min in the TCP coating bath. The conversion coating suppresses both anodic and cathodic currents, increases the polarization resistance, and provides both anodic and cathodic corrosion protection to the as-prepared alloy, as evidenced from potentiodynamic polarization curves and other electrochemical data. The TCP-coated specimens exhibited good corrosion resistance during a 14-day neutral salt-spray exposure with corrosion intensity values (g/m2-year) ~13x lower than values for the uncoated, as-prepared alloy specimens.