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topic 1471

Pretreating Aluminum for Painting without Chromate


I am looking for a method for preparing aluminum for painting that does not involve hexavalent chromium.

Currently, we use an alkaline pre-clean, clean water rinse and chromic acid (15%) treatment.

The pieces are aluminum housings to be used in television broadcasting studios. They will not be used outdoors or in corrosive environments. The paint is organic solvent-based spray paint.

Sending the pieces out would be the simplest solution but we want to keep the process in house for various reasons.

I appreciate any help.

Greg Richey


There are several papers being given at AESF-EPA week in Orlando the end of Jan.

Suggest that you call AESF and get a copy of the schedule and start calling the appropriate companies. They should bury you with information.

Excellent seminar. Go if you can.


James Watts
- Navarre, Florida


It sounds like a simple 3 stage or five stage iron phosphate treatment followed by a non-chrome seal or DI rinsing may be adequate for your purposes. Either could provide a good bonding surface for the paint and lots of household items including some used outdoors are pretreated this way.

The sequence for a three stage is:

1. Detergent Iron Phosphate w/ Fluoride
2. Rinse
3. Non-Chrome Seal or DI rinse

Five stage goes like this:

1. Alkaline Cleaner
2. Rinse
3. Iron Phosphate w/ Fluoride
4. Rinse
5. Non-Chrome Seal or DI rinse

Some paints work better with certain types of sealer, some don't need one at all. Remember that both the paint and pretreatment work together to provide the corrosion protection and performance that you want. Therefore, even a great pretreatment under a crappy paint may fail your criteria. Choose a quality paint finish.

Craig Burkart Craig Burkart signature
Craig Burkart
- Naperville, Illinois


I am looking for a quick method to paint aluminum extrusion, in a production enviorment. Any advice would be helpfull

Randy Simmons
- Vancouver, B.C.

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