Degradation Behavior of Arc-Sprayed Zinc Aluminum Alloy Coatings for the Vessel Yongle in the South China Sea

Since thermally sprayed zinc and aluminum coatings were invented 100 years ago, they have realized extensive industrial applications for steel structure protection in a variety of fields for nearly 100 years and have been proven to be effective and reliable. However, it has seldom been reported in the ship industry in China since many workers worry about the risk of rapid corrosion, especially in harsh environments such as the South China Sea. In this paper, three kinds of arc-sprayed zinc aluminum coatings were tested to choose the best coating system for application on the research vessel Yongle by electrochemical behavior and a long-term atmospheric exposure experiment. The variation of the corrosion rate and the bonding strength was used to clarify the long-term protection performance. The results show that Zn15Al has the lowest corrosion (Rp larger than 2200 Ω·cm2) among the three kinds of coatings and has a bonding strength larger than 6.38 MPa after a 5 year test. The performance of the coatings in the South China Sea indicates that they can provide excellent protection for the hull above the waterline of the Yongle vessel in the 3 year test. It could be predicted that thermally sprayed zinc aluminum coating has vast application potential in the South China Sea due to its excellent anticorrosion performance.