What must be done to faying surfaces and surfaces adjacent to the bolt head and nut?

Faying surfaces and surfaces adjacent to the bolt head and nut must be free of dirt and other foreign material to ensure a proper connection and load transfer. Clean surfaces allow for a more reliable grip and engagement between the structural elements, minimizing the risk of joint failure due to inadequate friction or interference. Contaminants can lead to poor bolt performance, which may compromise the integrity of the joint under load.

While lubricating surfaces can often be important in some applications to reduce friction, it is essential that these particular surfaces are clean first. Plating and painting might enhance corrosion resistance or add strength, but these measures are secondary to ensuring that the connection is solid and effective. When surfaces are not adequately cleaned, even the most advanced protection methods will not be effective in maintaining a reliable structural connection.