One of the most common ways of prepping metal is by blasting in order to remove any existing finish and smooth out a lot of the defects and create a more adhesive surface for powder coating. This would then be followed by washing/pre-treating the surface with products specifically formulated for the oils associated with your fabricating process in order to remove any dirt, dust, oil, or grease.
For this post, we used Simple Green All-Purpose Cleaner, but you can also use denatured alcohol. Most powder coating shops tend to put their parts through an extensive pre-treatment process
Having a clean surface is ABSOLUTELY VITAL when it comes to masking, especially when using adhesive tapes. This is the most common source of masking tape failure.