Silicone in Electrocoat Baths

Question: What happens to an electrocoat bath once silicones have entered it?


What happens to an electrocoat bath once silicones have entered it? If silicones are used and they are cured out, will they break down in the bath? I understand that all materials should be approved prior to use. Should it be a rule to keep silicones away from an electrocoat bath? G.B.


In general, silicones and paint (not just electrocoat) do not mix. I am assuming you are asking about silicone adhesive/sealants. While these products are excellent for their various applications, they will quite often cause contamination of parts that are painted with liquid coatings (solvent-borne, waterborne or electrocoat) and even powder coating. When the adhesive/sealants are fully cured, they probably pose less of a hazard, but a small amount of silicone contamination goes a long way.

Silicone comes in many forms. One of my former employers chased down silicone from three sources over several years: 1) An employee’s hand lotion that got transferred onto parts; 2) A mold release from some anti-fatigue floor mats used in the department; 3) A safety glass cleaner. The problem with some silicone contamination problems is that during the rework process (usually sanding and re-coating) the silicone may actually be spread to other parts. A former customer almost shut down a major appliance coating operation by drawing airborne silicone from the exhaust air from a sealant application area into the air-makeup system for the paint department. Another source of silicone is various silicone lubricants (grease, oil and spray types).

You asked about approval of materials. Most paint suppliers have a history of various contamination problems that they have experienced. Contact your current electrocoat material supplier.

Ironically, most fish-eye eliminators and some foam control products used by paint suppliers are actually silicones. However, they are very special “paint-compatible” silicones. They are usually very concentrated and need to be used sparingly. Problems, including loss of adhesion or intercoat adhesion, can result from excessive use of these products.