This first critical step in a satisfactory paint finish really starts with the condition of the part or surface to be coated and what steps were taken to prepare the surface for receiving a coating.
Has the part or surface been acclimated to the coating environment?
Apart brought in from a storage area, where there exists a difference in temperature from the coating material to be applied, may cause problems with adhesion or gloss and other surface defects.
Has the part or surface been properly cleaned, so as to be free of any oils from handling with bare hands, or other chemical contaminants from storage to process?
Many production facilities utilize compressed air to wash the part, or “blow off” the loose surface contaminants as a step in the preparation process. In addition, the part would typically be wiped clean with a suitable lint-free wipe and/ or tack cloth. Prepping the part for cleaning also requires an area, or location, that can have controlled clean air. Many facilities utilize Prep Stations, or Tack-off booths to accomplish this. Doing so also ensures a controlled environment where the dirt and debris from this process do not become potential sources of contamination elsewhere in the process.
Before the part can be coated, it will also require the removal of solid particulate that may remain on the surface. Wiping a surface clean is more than merely taking a handy rag and wiping it back and forth to get visible dirt and other particulates off of a surface. The prescribed method actually requires that all wiping is unidirectional from one side or end to the other. For instance, the decision on where to begin and end on an automotive part is usually from the most visible (class A surface) to the least visible (class B or C surface) aspect of that part. This would ensure any residual contaminant sources would be found on the least critical surface; should any remain. The requirement of wiping in one direction minimizes the probability of re-depositing contamination on to the surface.
Handling the parts, during and after the prep work, with lint-free gloves is a critical process requirement for many coating operations. Oils and particulate from human skin will contaminate the surface and create blemishes in the finish. We continuously shed small particles of skin and these can become airborne defects that can settle onto the surface throughout the process, so it’s always best to make sure that anyone inside the paint booth or prep area is dressed in appropriate attire.