1. Department of Materials Science and Engineering, Xi'an University of Technology, Xi'an 710048, PR China
2. CNPC Tubular Goods Research Institute, Xi'an 710077, PR China
3. Shaanxi Province Key Laboratory of Corrosion and Protection, Xi'an University of Technology, Xi'an 710048, PR China
4. State Grid Henan Electric Power Research Institute, Nanyang 450099, PR China