Preparation and research of structure-gradient and corrosion-resistant aluminium coatings on steel surface

Abstract

In order to control the composition and microstructure of corrosion-resistant aluminum coatings, a layer of pre-coating was deposited on Q235 steel surface by magnetron sputtering, and then corrosion-resistant aluminum coating with a certain thickness was prepared by hot dipping. Microstructure, thickness and chemical composition of aluminum coating were characterized by SEM equipped with EDS. The bonding strength of aluminum coating to substrate was tested by scratch test, and corrosion resistance was evaluated by salt water corrosion test. The results show that the coating obtained by magnetron sputtering combining with hot dipping is relatively denser. The aluminum coating prepared by both hot dipping and magnetron sputtering combining with hot dipping consists of an outer Al layer and an inner Fe-Al alloy layer. The thicknesses of Al layers are (45.75±6.41) μm and (44.84±3.17) μm, respectively. The thicknesses of Fe-Al alloy layers are (150.37±4.95) μm and (138.08±6.05) μm, respectively. The bonding strength between aluminum coating and substrate prepared by hot dipping is approximately 163.90N, while that prepared by magnetron sputtering combining with hot dipping is 160.25N. The corrosion mass loss rates of hot dip aluminizing Q235 steel and magnetron sputtering combining with hot dip aluminizing Q235 steel are about 1/12-1/6 of that of uncoated sample, and the corrosion pits of the latter one are more uniform.

Keywords

• hot dipping
• magnetron sputtering
• gradient structure
• aluminum coating
• bonding stren-gth
• corrosion resistance