Shot blasting using alumina grits is used to prepare the faying surface of the frictional grip connection by high strength bolts. Faying surface treatment with Inorganic Zinc-rich painting has been already used for such connection of steel structures and will be the effective method for aluminum structures that has superior corrosion resistance. The purpose of this study is to confirm the relationship between the slip coefficient and each the coating thickness of Inorganic Zinc-rich painting, and also the ground work treatment of aluminum surface. The present paper reports the results of above mentioned investigations. (l)When the ground work treatment of aluminum surface is ground with #80 grindstone before painting, slip coefficient can get more than 0.45. (2)The slip coefficient can get more than 0.45 even one side painting if it's process the above. In this case, another friction surface must do the grind stone finish (the grain size is greater than #180) or shot blasting finish using aluminum grits F36. (3)Thickness of paint influences slip load, and the most suitable thickness range is l00 to 200 micro meter. (4)If the thickness of paint is greater than 200 micro meter, the preload tension of bolt becomes lower than a case of thickness less than it.
