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Effect of Ti, Ni and Bi addition to the corrosion resistance of Zn hot-dip galvanized coatings

N. PISTOFIDIS1, G. VOURLIAS1,* , E. PAVLIDOU1, G. STERGIOUDIS1

Affiliation

  1. Physics Department, Aristotle University of Thessaloniki, Thessaloniki, 54124 Greece

Abstract

An usual phenomenon during zinc hot-dip galvanizing is the formation of coatings with extreme thickness and brittleness (Sandelin effect). This phenomenon is highly undesirable and for its inhibition titanium, nickel or nickel and bismuth are added in the zinc melt. The effect of these elements on the corrosion resistance of the zinc coatings is not yet investigated. In the present work the behavior of galvanized coatings containing 1%Ti, 1%Ni and 1%Ni-1%Bi was examined. The as-cast coatings were exposed in a Salt Spray Chamber, along with coatings deposited from a pure zinc bath for comparison purposes. The as-corroded coupons were characterized with Optical Microscopy, Scanning Electron Microscopy and X-Ray Diffraction. From this investigation it turned out that in every case the main corrosion products are hydrated zinc oxides and chlorides. Iron compounds were detected only at the final stage after 14 days of exposure. Pitting corrosion was also locally observed, but the predominant mechanism is uniform degradation. By contrast, the pure zinc coatings mainly suffer from pitting corrosion along with intergranular corrosion. In any case the corrosion performance after the addition of the alloying elements is enhanced..

Keywords

Galvanizing, Coating, Zinc, Alloying elements, Corrosion, SEM, XRD.

Submitted at: Nov. 14, 2006
Accepted at: June 15, 2007

Citation

N. PISTOFIDIS, G. VOURLIAS, E. PAVLIDOU, G. STERGIOUDIS, Effect of Ti, Ni and Bi addition to the corrosion resistance of Zn hot-dip galvanized coatings, Journal of Optoelectronics and Advanced Materials Vol. 9, Iss. 6, pp. 1653-1659 (2007)