Preparation and performance of a Pd-Co gradient coating on stainless steel

A Pd-Co gradient coating is prepared on stainless steel by simply controlling the electro-deposition current density in the same electrolyte bath. SEM, EDX, XRD, weight loss test and some other methods were used to determine the properties of the Pd-Co gradient coating. The result shows that Co content in the coating increases from about 24 at.% at the substrate/coating interface to about 36 at.% at the outside surface by changing the deposition current density. The coating is uniform, compact and the grain size decreases from the inner interface to the outside surface. Compared with coatings deposited at constant current densities, the Pd-Co gradient coating shows relatively higher micro-hardness, higher adherence strength to the substrate, lower internal stress and lower porosity. As the result, in stirred boiling acetic acid (90 wt%) and formic acid (10 wt%) mixtures containing 0.005 M Br− and solid particles, the gradient coating coated stainless steel samples show quite good erosion-corrosion resistance.