Effect of structure, phase, and elemental composition of AlN, CrAlN, and ZrAlN coatings on their electrochemical behavior in 3% NaCl solution

Abstract

Thin coatings AlN, AlZrN, and AlCrN were deposited by pulsed magnetron sputtering. The high‐speed steel Т1, structural alloy steel 5140, and structural carbon steel 1017 were used as substrates. The magnetron current, nitrogen content in the gas mixture, and bias voltage on the substrate were changed to obtain nanostructured and amorphous layers of coatings with different elemental compositions. The voltammetry and impedance spectroscopy were performed on the coated samples in 3% NaCl solution. The corrosion behavior of the coatings was characterized by the corrosion current density icorr, the polarization resistance Rp (at the corrosion potential), the ratios icorr,s/icorr, and Rp/Rp,s, where subscript s refers to the substrate. It was shown that the coatings under study (except AlN) are electrochemically active, and the corrosion processes occur not only on the substrate in the coating discontinuity but on the coating surface as well. The coatings AlN/T1, AlZrN/5140, AlCrN/T1, and AlCrN/5140 with icorr ~ 10−7 A cm−2 are found to be the most corrosion‐resistant in 3% NaCl. The paper discusses factors affecting the corrosion behavior of the investigated coatings.