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 i corr, the polarization resistance R p (at the corrosion potential), the ratios i corr,s /i corr , and R p /R p,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 i corr ~10 −7 A cm −2 are found to be the most corrosionresistant in 3% NaCl. The paper discusses factors affecting the corrosion behavior of the investigated coatings.3% NaCl solution, coatings AlN, AlZrN, and AlCrN, structure and electrochemical behavior | INTRODUCTIONRecently, much attention has been paid to the development of nanostructured coatings with high physical, mechanical, and tribological properties. Such coatings include ZrMN and CrMN (M = Al and Ti) with a hardness of more than 40 GPa; they are simultaneously characterized by thermal and corrosion resistance. In recent years, coatings ZrAlN, CrAlN ZrTiN, and CrTiN with hardness 30-40 GPa are attracting the most attention due to their unique properties, including high hardness, high-temperature oxidation resistance, minimal wear, and excellent thermal stability. [1][2][3][4][5][6] The TiAlN coating exhibits inferior corrosion resistance compared to the TiN coating. Potentiodynamic polarization measurements have shown that for all single layer CrN, TiN, TiAlN coatings, and multilayer nanolayered TiAlN/CrN coatings, the corrosion potential is shifted to higher values compared to the uncoated substrate. The corrosion current density for coated samples decreases. The protective effect of multilayer TiAlN/CrN coatings is higher than that of single-coat coatings. The Nyquist and Bode plots obtained from the EIS measurements were fitted with appropriate equivalent circuits to calculate coating discontinuity resistance, charge transfer resistance, and capacitance. [7] These studies confirm that

Synthesis and Characterization of Polypyrrole/Fe3O4 Nanocomposites: A Promising Material Against Carbon Steel Corrosion

“…The coating layer thickness was (147 ± 31) µm and the whole tested area of the working electrode was 10.2 cm 2 . The coated samples were immersed in 3 wt% NaCl solution at room temperature for 0 to 20 h. This concentration of the solution was chosen as a standard value reported in several previous works [22][23][24][25][26] .…”

Dependence of protective effect of Ti1–xAlxN coatings in 3 wt.% NaCl solution on dissolution mechanism of their phases c‐Ti0.5Al0.5N, c‐AlN, and c‐TiN

“…[ 8 ] The AlN coating has a corrosion current density of 0.18 μA cm −2 and the polarization resistance at the corrosion potential R p = 360 kΩ·cm 2 . [ 9,10 ]…”

“…Ti 1– x Al x N coatings' corrosion resistance depends on structure, thickness, phase composition, Al content, and microdroplets. [ 9,10,24 ]…”

“…AlN coating has a corrosion current density of 0.18 μA cm −2 and the polarization resistance at the corrosion potential R p = 360 kΩ•cm 2 . [9,10] Ti-N compounds comprise three different phase regions depending on the N content: α-Ti up to N/ Ti = 0.2, Ti 2 N for 0.2 < N/Ti < 0.6, and Ti 1-x N x for N/Ti ≥ 0.6. In the literature, there are no references to intermediate amorphous stages in the series α-Ti (N)→Ti 2 N → TiN.…”

“…Ti 1-x Al x N coatings' corrosion resistance depends on structure, thickness, phase composition, Al content, and microdroplets. [9,10,24] In this study, Ti 1-x Al x N coatings were deposited by impulse magnetron sputtering (IMS) and CAE on various substrates to change their stress and structural state at the initial stage of formation, to change phase composition, Al content, and its ratio to Ti, as well as the texture degree. The purpose of the study is to describe the dissolution mechanism of the Ti 1-x Al x N coating in a 3 wt.% NaCl solution, depending on the ratio of the cubic nitride phases c-AlN, c-TiN, and c-Ti 0.5 Al 0.5 N, the intermetallic phase ε-Al 2 Ti, and hexagonal h-Ti metal phase, as well as the element ratio, porosity, total formation energy, residual and oriented stresses, defects, crystallite size, and oxide films composition.…”