Preparation Of Silane Treatment Agent On Galvanized Sheet Surface And Its Film Forming Properties

Galvanized steel is one of the excellent products of iron and steel materials,which has outstanding processing and using property,as well as the corrosion resistance in the dry environment.But pure zinc is very easily corroded in the wet air,so actions must be taken on the galvanized surface to improve its corrosion resisitance.In the past,the most useful method is chromate passivation,but chromate is poisonous.Now the the silane treatment is widely used,However,the hydrolysate of silane coupling agent is unstable,which has caused some restriction for its industrial applications.SCA KH550,KH560,BTSE were selected.The stablity of hydrolysate of the three kinds of SCA and KH560/KH550,KH560/BTSE were researched.The results show that the hydrolysate of the KH560/BTSE has excellent stablity,it can be stored for 150 days.The silane film of KH560/BTSE is tested,the results show that the corrosion resistance of KH560/BTSE mixed film is better than untreated galvanized steel.The neutral salt spray tests show that the KH560/BTSE film got no rust within 24 h.However,due to the lack of flexibility of the silane film,the surface of the film has obvious cracks,and the film is thick.In order to enhance the corrosion resistance of silane film,acrylic resin and silica sol were added into the KH560/BTSE mixed hydrolysate to make up acid composite silane solution.The acid composite silane film was tested,the results shows that the film got no rust within 120 h in neutral salt spray,the structure of the film layer is homogeneous without cracks on its surface and its corrosion resistance is improved.The acrylic resin was involved in the film formation process and the film thickness is 17 μm.The alkaline composite silane solution was made up by adding polyurethane resin and silica sol to BTSE/KH560 mixed silane hydrolysate.The alkaline composite silane film was tested,the results shows that the film got no rust within 150 h in neutral salt spray,the structure of the film layer is homogeneous without cracks on its surface and its corrosion resistance is substantially improved.The polyurethane resin was involved in the film formation process and the film thickness is 22 μm.