Preparation of alumina coatings on metallic nickel substrate using a room-temperature wet chemical pretreatment method

Electrodeposited nickel substrate was effectively micro-roughened with an acidic bath containing 5 wt% H₂SO₄ and 10 wt% (NH ₄)₂S₂O₈ at room temperature. The uniformly roughened surface was then sequentially wash-coated with boehmite sol and alumina slurries. The microstructure and the surface performance of the wash-coat/substrate were investigated by scanning electron microscopy and ultrasonic vibration test. The nickel substrate that was etched for 3 min at room temperature yielded a foam-like roughened surface morphology with a high large surface area. A crack-free primer coating and a slurry coating with very little tiny crack can be prepared by using this convenient, energy-saving, and time-efficient pretreatment method.