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.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Allegra L and Zoccola J C 1983Mater. Perf. 22 5
Borzillo A R and Horton J B U.S. Patent 3,343,930
Borzillo A R and Horton J B U.S. Patent 3,393,089
Dalledone E, Adolfo Barbosa M and Wolynec S 1995Mater. Perf. 34 24
Horton J B 1978Corrosion control by coatings (Princeton, NJ: Science Press) p. 59
Johnsson T and Kucera V 1982Proc. int. conf. on hot-dip galvanising, Intergalva ’82 (London: European General Galvanisers Association (EGGA)) 47/1
Li Y 1999Corrosion mechanism and reinforced protection of hot-dipped coated steel wire in seawater, Ph.D. Dissertation, Northeastern University, Shenyang
Pelerin Jet al 1982Proc. int. conf. on hot-dip galvanising, Intergalva ’82 (London: EGGA) 48/1
Sun H Yet al 1997Proc. 10th Asia pacific corrosion control conference (Bandung: Indonesia Corrosion Association) D6.1/6
Townsend H E and Zoccola J C 1979Mater. Perf. 18 13
Townsend H E and Meitzner C F 1982Proc. int. conf. on hot-dip galvanising, Intergalva ’82 (London: EGGA) 46/1
Townsend H E and Borzillo A R 1996Mater. Perf. 35 30
Zoccola J Cet al 1978Atmospheric factors affecting the corrosion engineering materials-ASTM STP 646 (Philadelphia, PA: ASTM) p. 165
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Li, Y. Corrosion behaviour of hot dip zinc and zinc-aluminium coatings on steel in seawater. Bull Mater Sci 24, 355–360 (2001). https://doi.org/10.1007/BF02708631
Received:
Revised:
Issue Date:
DOI: https://doi.org/10.1007/BF02708631