316L stainless steel coatings on ZE41 magnesium alloy using HVOF thermal spray for corrosion protection

Stainless steel coatings have been applied on the surface of ZE41 magnesium alloy using High Velocity Oxygen-Fuel as deposition technique to improve the corrosion performance. Some parameters of the thermal spraying process have been studied (spraying distance, number of layers and gun speed) to produce homogeneous and protective coatings without deteriorating the low melting temperature substrate. Homogeneous, crack-free, fully dense coatings with thicknesses in the range of 42-478 μm were obtained. Electrochemical corrosion tests were used to test the corrosion protection effectiveness of the different coatings. Two of the sprayed stainless steel coatings were capable of protecting the magnesium substrate for 7 days in contact with 3.5 wt.% NaCl aqueous solution, with corrosion resistances close to bulk stainless steel. After 48 days of immersion, one coating was still an effective corrosion barrier for the magnesium substrate, without any sign of substrate degradation. A corrosion mechanism for each tested specimen has been proposed.