Silicone in Electrocoat Baths

Question:

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.

Answer:

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.