Effect of Overspray and Incomplete Masking of Faying Surfaces on the Slip Resistance of Bolted Connections

Despite precautions taken to protect contact areas during painting, some overspray from painting of surfaces adjacent to faying surfaces may take place. Although current specifications permit the use of certain coatings, such as hotdip galvanizing, inorganic zinc-rich paints and metalized zinc or aluminum on the surfaces of friction connections, the paint used on the remainder of the structure could be of the type which is not acceptable for use on faying surfaces. The effect of this inadvertent coating of the faying surfaces is not known. It has been suggested that the degree to which overspray affects the slip performance of friction-type connections depends on the average overspray paint film thickness, regardless of the type of paint used. Overspray, however, is not a true paint coating and is, therefore, very difficult to establish a film thickness, as suggested by Ref. 2. This paper deals with the results of an experimental project sponsored by the American Institute of Steel Construction and the Research Council on Structural Connections (RCSC) carried out at the University of Texas- Austin to study the effect of overspray on the faying surfaces of friction-type connections. More specifically, the objectives of this project are to determine the slip performance of friction-type connections under the influence of: (a) overspray on the faying surfaces, and (b) incomplete masking of the faying surfaces.