There are a variety of methods that will clean and remove
soils from metals. The pretreatment method used is determined by the part to be
coated (size, configuration, material), the type of soil to be removed (dust,
wax, oil, etc.), and the performance requirements of the finished product. This process of pretreatment requires three
steps. The first two steps are explained
in detail below, and look for the third step in a later blog.
1. CLEANING
Mechanical cleaning
– includes methods like scratch brushing and sand blasting. This abrasive
action not only removes the surface impurities but also eliminates scratches
and surface irregularities. Mechanical
cleaning is sometimes the only way to remove excessive dirt, rust, or scale but
can be labor intensive and expensive.
Chemical cleaning – includes removal of dirt, oil, and grease
present on the surface by means of chemicals. The chemicals may be applied by
wiping, spraying, or dipping, which depends on the soils to be removed, the size and type of the
part, the type of coating to be applied, and the substrate material.
2. RINSE
Proper rinsing
between process stages removes any remaining contaminated solutions from the
substrate surface and is essential for successful pretreatment and coating
performance.
Pretreatment is
the base for powder coating. The highest quality powder coating will show you
excellent results ONLY if the pretreatment is done correctly, maximizing
the benefits of powder coating. Oily
patches, pin holes, rust spots, reduced resistance to weather, and overall poor
powder coating performance will result with improper pretreatment.