Tips for Removing Rust by Sandblastingby John Stevens J.D.
Sandblasting, if done properly, is one of the most effective ways to remove rust. However, it is extremely messy and can even damage the underlying metal. Thankfully, removing rust with a sandblaster is relatively simple with an understanding of a few basic tips. As an initial matter, however, the importance of wearing safety goggles, heavy gloves and a respirator designed to filter the sand cannot be stressed enough.
Minimizing the Mess
One of the biggest criticisms about sandblasting is that it is extremely messy. There is simply no way to eliminate the mess created, but it can be minimized. Because sand particles are so small, they can easily enter small cracks and crevices, going undiscovered for years. The best way to minimize this is to tape off as many areas as can reasonably be reached. Large areas can be covered with a tarp or cardboard and taped down.
Angling the Spray Nozzle
As the sand strikes the rusted metal, it literal scrapes off the rust particles. One of the most common mistakes is to point the propelled sand directly onto the face of the rusted surface. The rust will eventually be removed, but it will take longer than if the spray nozzle were instead pointed at a slight angle to the rust. Rust does not develop evenly meaning it forms peaks and valley. By angling the nozzle, the sand is able to strike and grab onto these peaks and valleys from the side and quickly wear them down.
Avoiding Metal Warping
Prolonged exposure to pressurized sand can easily warp metal. This is because as the sand particles strike the metal, they create friction, which in turn creates heat. As the metal heats up, it expands, typically outward. Metal warping is almost impossible to detect while blasting, unless the metal produces a loud "pop" sound. For this reason, the warped metal is not discovered until the sandblasting process is complete. As a result, although the rust has been removed, a new problem now exists. To avoid warping the underlying metal while sandblasting, avoid sandblasting the same portion of metal for more than a couple of seconds and allow that portion a few seconds to cool before blasting again.
Avoiding Clogs in Air Line
Sandblasting is nothing more than propelling sand at a high rate of speed with compressed air. Compressed air contains moisture. The higher the humidity in the environment, the more moisture in the sandblasting tank. This moisture, mixed with the sand in the tank, causes the sand to resemble clay. This clay can quickly clog the hose used by the sandblaster once it dries. To remedy the problem, it is necessary to disconnect and thoroughly clean the air line. However, the problem can often be avoided entirely by clearing the sand out of the sandblaster's air line between uses. To clear the line, first disconnect the air compressor from the sandblaster, then flip the switch on the sandblaster that feeds the sand into the air line. Open the spray nozzle to quickly expel the air within the compressor and any sand remaining in the air line.