Corrosion Resistance of Ni-P Gradient Coatings in 3.5% Sodium Chloride Solution

The high innerstress, low bindingforce and poor wear resistance of electroless Ni-P coatings can′t meet the special needs of corrosion resistance of some wear parts yet.In this work, low-P, middle-P, high-P and l-m-h Ni-P gradient coatings were prepared on the surface of 45# steel by electroless plating. The thickness of coatings were measured by cross section metallographic method and the corrosion resistance of four coatings were investigated by linear polarization method and immersion test. The results show that the gradient coatings present better corrosion resistance in 3.5% NaCl solution than homogeneous coatings,and the pitting corrosion resistance is superior to the homogeneous coatings obviously.