First, determine what you’ll be coating the most often. If you are coating sheet steel, for example, you will usually only need light oil cleaning. Angle iron or castings often need sand/shot blasting to remove scale and surface rust. Aluminum is prepared differently than galvanized or regular steel; the oxidation layer of aluminum must be removed, which requires certain chemicals that provide a good etched layer for paint adhesion. Identifying which type of cleaning is right for your process is the first step in long-lasting, quality results.
The most common types of metal cleaning are:
Blasting. Blasting with sand or shot is a great way to clean up metal scale, laser scale, rough welds, or heavily rusted steel. Blasting is also used to strip off previously coated metal for refinishing. While blasting smooths out a lot of surface defects in raw metal, it does not fully clean the metal of oils or other contaminants. However, blasting does create a more adhesive surface for the powder coating after the part has been cleaned of residual soils.
Washing. Pressure washing, dipping, or automatic washing (with a soap specifically formulated for the soils specific to your fabricating process) are the most effective ways of cleaning the metal prior to the next finishing stage. Steam cleaning or hot water helps break down the oils and can reach difficult spots or gaps in the surface. Detergent is the best way of cleaning metal of oils, waxes, polishing compounds, or other substances that will prevent the powder from sticking to the metal.
Wiping. Solvent wiping is another way to clean up the metal of surface oils and contaminants, but it is an inaccurate way to clean. Since the part is manually wiped with white linen rags, the rags can become saturated with the oil you are trying to remove.