Wear and corrosion resistance of heat treated and as-plated Duplex NiP/NiB coatings on 2024 aluminum alloys

Abstract

Al–Cu–Mg (Grade 2024) aluminum alloy was plated with nickel–boron coatings by the electroless deposition method. Some of the coatings were submitted to a hardening heat treatment specifically designed for electroless nickel coated aluminum alloys, with the following conditions: 180°C — 4h; in an atmosphere containing 95% Ar and 5% H2.Uncoated aluminum, treated and untreated samples were submitted to the Taber abrasion test to assess their wear resistance. The wear track was then examined by SEM and roughness measurement. The wear resistance of the coated samples was quite good, with a Taber Wear Index of 28.5 before heat treatment and 24 after (obtained with CS-17 wheels).The corrosion resistance of the samples was investigated by the way of polarization and electrochemical impedance spectroscopy (EIS) and the influence of the heat treatment was observed. Corrosion resistance of the system is good, with a corrosion potential close to −250mV, and heat treatment improves it slightly.Taber abrasion tests were used to simulate erosion of the coatings during use. Worn coatings were then submitted to electrochemical tests to assess conservation of corrosion resistance during use of coated samples. Only a slight decrease of the corrosion resistance was observed.