Light Coverage Powder Coat

Ask an Expert From: Products Finishing, , from Powder Coating Consultants, Div. of Ninan, Inc.

Posted on: 7/1/2004

Question: We use a black-texture powder coat that might be two mils thick and very fine textured.

Question:

We use a black-texture powder coat that might be two mils thick and very fine textured. Normally our machined and lightly sanded surfaces coat well. However when we take a sandblasted surface and sand it down towards a smoother textured surface the powder does not blend the two areas well at all and even creates a different reflection that is so obvious. I am having no luck at all convincing the machine shop people that I need a surface with a consistent appearance for the coating to work. Since 95% of my product line works well with the current coating, can you spell out the facts of life for my people so I can get the cooperation I need? Or refer me to an industry standard for light coverage?

Filler question: we use Devcon titanium putty 1076D for porosity filling on these same powder coated parts and it sometimes fails. If all instructions are followed for mixing and cure time along with properly cleaned parts should this formula work at all times for the wash and paint cycles? The usual recommended fillers require a high heat cure, which we cannot do in-house. A. L.

Answer:

Surface inconsistencies of a particular substrate can “telegraph” through a particular powder coating. This is especially true with smooth, high-gloss powders. However, textures were developed to “hide” surface inconsistencies. They hide surface defects in several ways. For one, textures are applied typically thicker than smooth powders (3.0-5.0 mils vs. 1.5-3.0 mils). Secondly, most textures do not reflect light very well and are, therefore, considered low-gloss materials.

Your problems can be caused by the fact that the surface irregularities are deeper than the powder thickness. Secondly, you are applying the textured powder at a film thickness that is much lower than normal (check this one with your powder formulator). Finally, a fine texture will not hide surface defects as well as a coarser texture, so maybe you can change the powder formulation.

You can tell your colleagues, that even though a textured powder coating is designed to help hide surface inconsistencies, it is not considered a filler material. They must provide you a surface that you can cover with a reasonable amount of surface coating and still produce a visually acceptable part. Tell them that powder coating is a surface coating just like any other “paint” and not some miracle filler/coating product. As for your second question, we have had great success using Lab Metal as a filler material. Their contact information is available through PF Online (www.pfonline.com).

 



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