EFFECT OF MICROSTRUCTURE OF FERROUS SUBSTRATE ON POROSITY OF ELECTROLESS NICKEL COATING

The corrosion resistance of electroless nickel (EN) coatings on ferrou s substrates is affected by coating porosity, Carbon and iron carbide are present in the microstructure of ferrous alloys, If the sites of c arbon and iron carbide are not as catalytically active to EN depositio n as the rest of substrate surface, there is a possibility of pore for mation on these sites, In the present study, the rate of EN deposition on carbon, iron carbide and steel surfaces was individually measured, The locations of EN deposits on the microstructure of a ferrous alloy mere mapped with the SEM/EDS technique and compared to the locations of carbon on the original substrate surface, This paper summarizes the results of these investigations.