Electroless Ni-W-P/Ni-B duplex coatings on AZ91D magnesium alloy

The Ni-W-P/Ni-B duplex coatings were deposited on AZ91D magnesium alloy by electroless plating and evaluating their structure, morphology and corrosion resistance. The duplex coatings were deposited in dual baths (alkaline hypophosphite- and borohydride-reduced electroless nickel baths). The coatings were amorphous in as-plated condition. Upon heat-treatment, they were crystallized and produced nickel borides. Thus, the Ni-W-P/Ni-B duplex coatings with good corrosion resistance properties were obtained in protecting AZ91D magnesium alloy and expanding their scope of applications.