Corrosion Resistance Behavior of Single-Layer Cathodic Arc PVD Nitride-Base Coatings in 1M HCl and 3.5 pct NaCl Solutions AKEEM YUSUF ADESINA, ZUHAIR M. GASEM, and ARUMUGAM MADHAN KUMAR The electrochemical behavior of single-layer TiN, CrN, CrAlN, and TiAlN coatings on 304 stainless steel substrate, deposited using state-of-the-art and industrial size cathodic arc PVD machine, were evaluated in 1M HCl and 3.5 pct NaCl solutions. The corrosion behavior of the blank and coated substrates was analyzed by electrochemical impedance spectroscopy (EIS), linear polarization resistance, and potentiodynamic polarization. Bond-coat layers of pure-Ti, pure-Cr, alloyed-CrAl, and alloyed-TiAl for TiN, CrN, CrAlN, and TiAlN coatings were, respectively, first deposited for improved coating adhesion before the actual coating. The average coating thickness was about 1.80 lm. Results showed that the corrosion potentials (E corr ) of the coated substrates were shifted to more noble values which indicated improvement of the coated substrate resistance to corrosion susceptibility. The corrosion current densities were lower for all coated substrates as compared to the blank substrate. Similarly, EIS parameters showed that these coatings possessed improved resistance to defects and pores in similar solution compared to the same nitride coatings developed by magnetron sputtering. The charge transfer resistance (R ct ) can be ranked in the following order: TiAlN > CrN > TiN > CrAlN in both media except in NaCl solution where R ct of TiN is lowest. While the pore resistance (R po ) followed the order: CrAlN >CrN >TiAlN >TiN in HCl solution and TiAlN > CrN >CrAlN >TiN in NaCl solution. It is found that TiAlN coating has the highest protective efficiencies of 79 and 99 pct in 1M HCl and 3.5 pct NaCl, respectively. SEM analysis of the corroded substrates in both media was also presented. DOI: 10.1007/s11663-016-0891-7 Ó The Minerals, Metals & Materials Society and ASM International 2017 I. INTRODUCTION PHYSICAL vapor deposition (PVD) techniques used for deposition of hard transition metal nitride (binary, ternary etc.,) coatings e.g., TiN, CrN and TiAlN, CrAlN are well known for their improved wear resistance, high hardness, lower coefficient of friction, thermal stability, chemical inertness, and corrosion resistance. [1–6] These characteristics have made them suitable candidates for application in different harsh environmental condi- tions [2] such as in cutting tools, turbine blades, molds, and dies. Cathodic arc deposition process is a PVD technique which offers very high deposition rate and produces coatings with excellent adhesion to the sub- strates. [7] However, defects, such as pinholes and micro-pores due to nitride layer columnar growth as well as inclusion from liquid droplets resulting into macro-particles within the coating, impair their corro- sion resistance behavior. [5,8] This is because defects create a solution path between the coating and the substrate thereby compromising the effectiveness of resistance against charge transfer. [3,9] For this and other reasons, arc and plasma technologies are constantly being improved to ultimately enhance coating properties by reducing macro-particles, increasing deposition rate etc. Wen-Jun Chou et al. [10] study the behavior of TiN coatings on 304 SS in 5 pct NaCl and 1M H 2 SO 4 + 0.05 M KSCN solutions. Using the standard salt spray and potentiodynamic polarization (PDP) test, they deter- mined the critical coating thickness in the NaCl and H 2 SO 4 solutions to be 0.7 and 0.3 lm, respectively. When the coating thickness is smaller than the critical thickness value corrosion current abruptly increased. Electrochemical impedance spectroscopy (EIS) and PDP were used to evaluate the corrosion resistance of TiN and TiAlN coatings on a martensitic stainless steel in 0.5 mol/l NaCl and 1 mol/l H 2 SO 4 solutions by Yang Li et al. [1] They found that TiAlN coating present better corrosion resistance stability after 100-hour immersion than TiN coating, attributing the corrosion mechanism to adhesive failure of the coating. Also, Korablov et al. [11] studied the hydrothermal corrosive behavior of commercial TiAlN and CrN coatings for a range of AKEEM YUSUF ADESINA and ZUHAIR M. GASEM are with the Mechanical Engineering Department, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia. ARUMUGAM MADHAN KUMAR is with the Center of Research Excellence in Corrosion, Research Institute, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia Contact e-mail: adesina@kfupm.edu.sa Manuscript submitted August 20, 2016. Article published online January 5, 2017. METALLURGICAL AND MATERIALS TRANSACTIONS B VOLUME 48B, APRIL 2017—1321