Abstract
Phosphatation is a well-known technique to improve friction and wear behaviour of zinc coated steel, but has a variety of economic and ecologic limitations. In this study an alternative coating based on ammonium sulfate ((NH4)2SO4) is applied on skin-passed hot-dip galvanized steel sheets in order to investigate its surface chemical and tribological behaviour in a Pin-on-Disk Tribometer. Raman- and X-ray photoelectron spectroscopic results revealed a formation of ammonium zinc sulfate ((NH4)2Zn(SO4)2 * xH2O) on the surface, which is primarily located in the skin-passed areas of the steel material. Sulfate coated samples exhibited a superior friction behaviour in Pin-on-Disk Tests using squalane as a model substance for oil-like lubricated conditions and a formation of a thin lubrication film is obtained in the wear track. Squalane acts as a carrier substance for ammonium zinc sulfate, leading to an effective lubrication film in the wear track.
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