Relationship Between Pretreatment and Initial Deposition in Electroless Nickel Plating on Aluminum Substrate

摘要

Studies were conducted using the double zincate method on the surface morphologies of aluminum substrates at each stage from pretreatment to electroless nickel plating, on the structure of immersion zinc-iron deposits and on the initial deposition process of electroless nickel plating on aluminum. A large number of zinc crystals about 1 #mu#m in diameter were deposited by displacement plating after the first zincate stage, and island-like protuberances were observed on the aluminum surface after stripping of the zinc crystals. It was confirmed that zinc crystals were formed on the tops of the protuberances prior to the flat aluminum surface during the second zincate displacement reaction.The zinc crystal formed in both the first and second zincate processes contained about 1 wt percent of iron.The structure of the initial electroless nickel deposition layer was studied by TEM of cross sections prepared by ultramicrotomy. The presence on the zinc crystal surface of a layer that appeared to be pure nickel, acting as a center of autocatalytic reaction was confirmed.