Surface profile is defined as a measurement of the maximum peak-to-valley depth created by abrasive impingement against a surface during abrasive blast cleaning operations, or by an impact-type power tool. During abrasive blast cleaning, the mass of the abrasive and the velocity of the abrasive movement created by compressed air generates kinetic energy (the abrasive can reach speeds approaching 600 miles per hour as it exits the blast nozzle). When the abrasive impacts the surface, it cuts into the surface (angular abrasives) or peens the surface (round abrasives) and creates a series of peaks and valleys in the surface.
Creating a peak-valley pattern in the surface of the steel effectively increases the surface area, providing an anchor for the coating system. The anchor must be adequate to prevent the coating from becoming detached as it undergoes shrinkage stresses during drying and curing. It must also be adequate to assure that the coating remains attached during service. Both the structure and the coating system protecting the structure will move while in service. This movement may be caused by expansion and contraction of the substrate due to temperature fluctuation, or live loads placed onto a structure; for example, vehicles crossing a bridge; any of which can stress the bond between the substrate and the coating protecting it. The surface profile must be compatible with the coating system. Typically, the higher the coating system thickness the greater the surface profile depth that is required to anchor the system to the substrate.
Test your knowledge of surface profile by challenging each of the 10 questions below. Helpful references are included in the questions, and a full answer key can be found at the end of the quiz.