The deposition of stannate chemical conversion coatings on AZ91 D magnesium alloy by using the potentiostatic technique was investigated to improve uniformity and corrosion protection performance of the coating film. It was found that anodic polarization during the stannate conversion process accelerated dissolution of magnesium ions and promoted deposition of the coating film. Optimal polarization potential was explored as a function of corrosion protection performance evaluated by potentiodynamic polarization curves in borate buffer solution. Scanning electron microscope observation and electrochemical corrosion tests of the stannate-coated samples confirmed significant improvement in uniformity and corrosion resistance of coatings deposited by the potentiostatic technique compared to those of coatings deposited by the simple immersion method. (C) 2007 Elsevier Ltd. All rights reserved.