• Corrosion behaviour of hot dip zinc and zinc-aluminium coatings on steel in seawater

    • Fulltext


        Click here to view fulltext PDF

      Permanent link:

    • Keywords


      Galvanization by hot dipping; Zn–Al alloy coating; seawater corrosion; pitting corrosion; cathodic protection.

    • Abstract


      A comparative investigation of hot dip Zn–25Al alloy, Zn–55Al–Si and Zn coatings on steel was performed with attention to their corrosion performance in seawater. The results of 2-year exposure testing of these at Zhoushan test site are reported here. In tidal and immersion environments, Zn–25Al alloy coating is several times more durable than zinc coating of double thickness. At long exposure times, corrosion rate for the Zn–25Al alloy coating remains indistinguishable from that for the Zn–55Al–Si coating of similar thickness in tidal zone, and is two to three times lower than the latter in immersion zone. The decrease in tensile strength suggested that galvanized and Zn–55Al–Si coated steel suffer intense pitting corrosion in immersion zone. The electrochemical tests showed that all these coatings provide cathodic protection to the substrate metal; the galvanic potentials are equal to – 1,050, – 1,025 and – 880 mV (SCE) for zinc, Zn–25Al alloy and Zn–55Al–Si coating, respectively, which are adequate to keep the steel inside the immunity region. It is believed that the superior performance of the Zn–25Al alloy coating is due to its optimal combination of the uniform corrosion resistance and pitting corrosion resistance. The inferior corrosion performance by comparison of the Zn coating mainly results from its larger dissolution rate, while the failure of the Zn–55Al–Si coating is probably related to its higher susceptibility to pitting corrosion in seawater.

    • Author Affiliations


      Yan Li1

      1. Institute of Oceanology, Chinese Academy of Sciences, Qingdao, 266071, China
    • Dates

  • Bulletin of Materials Science | News

    • Dr Shanti Swarup Bhatnagar for Science and Technology

      Posted on October 12, 2020

      Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
      Chemical Sciences 2020

      Prof. Surajit Dhara — School of Physics, University of Hyderabad, Hyderabad
      Physical Sciences 2020

    • Editorial Note on Continuous Article Publication

      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

© 2022-2023 Indian Academy of Sciences, Bengaluru.