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-----LOW COST PRETREATMENTS FOR ALUM. EXTRUSIONS USED IN BENIGN ENVIRONMENTS
I am looking for information on low cost pretreatments for aluminium extrusions prior to Epoxy Polyester powder coating in a gas fired convection oven. Chromate conversions are fine for extreme environments but are costly and my finished products are only for use in office or hospital environments. Please help.
Len Patterson- ENGLAND
1999
The best process is using conversion coating uses no chrome conversion coating.
Recently there are some processes based on other metals which can convert Aluminium quite successfully without the obligation to have Chrome solution. The problem with those environmentally friendly solutions is that they are less corrosion resistant, but in your case it is enough.
Yehuda Blau
YB Plating Engineering and Quality - Haifa Israel
1999
1999
Dear Mr Patterson,
Just came back from holiday and saw your question concerning pretreatment of aluminum parts prior to powder-coating.
I agree, Chromating these parts for inside exposure would be overdone normally. Also the chrome causes environmental and health problems. We here in the Netherlands came to the same conclusion. I know of several plants here that work with, depending of the use of the finished parts,
a) either no conversion at all or
b) a conversion layer using other metals than chrome.
In the first case we reached over 1500 hours salt spray on aluminum profiles and epoxy powder coated. In the latter case there exist pretreatment systems that have for example the Qualicoat and/or GSB approval, which means they are officially allowed on aluminium building parts.
I would be glad to give you more info if needed. Please contact.
Remmelt Bosklopper
- Enschede, The Netherlands
Zinc Phosphate would be my first choice followed by iron phosphate as a second if zinc is a problem for you. You seem to be looking more for adhesion than corrosion resistance. Zinc has better adhesion properties than iron however I have used both. I have also used "wash" primers, the so called acid etch primers for pretreatment which have the benefit of being able to be sprayed on. There are phosphoric acid/water spray systems which also work well.
Ward Barcafer, CEFaerospace - Wichita, Kansas
1999
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