How to Paint Over Aluminum?

Aluminum is a challenge to paint. Paint has a hard time adhering to aluminum. Typically, a caustic primer is used after a careful surface prep. I don't know who does the primer, but it is very caustic.

Powder coating may work better, but surface prep is important. Sandblasting (or bead blasting with glass beads) can have a desirable effect of creating some tooth for paint, but it is more likely to create a dull finish that gets dirty easy and does not come clean.

Another thought is to anodize the aluminum, which gives a harder finish than paint and I think more impervious to the salt and climate of Florida. There are two types of anodizing. One is the standard and the other is much thicker and expensive. You probably can buy new chairs for the cost of anodizing, maybe several more chairs. Powder coating is not cheap, either.

I probably would buy PVC chairs. That has worked for us without degradation over the years. It is not as ornate as wood or metal, but very robust.

Sandblasting works fine. A little expensive for a chair, but maybe they're expensive chairs. As noted, anodizing is a great surface prep. I've used a chromate primer followed by a baked paint finish with some success.

Here's another vote for Chromate Primer on aluminium. It is normally yellow in colour.

We also use an etching primer that leaves a yellow hue to the aluminium. Without it the paint just falls off as it really does not like sticking to aluminium.

Google etching primer for local results.

We are targeting to treat about 35 chairs a week, even if it is a small operation, it runs continuosly, so we could invest in a small sandblasting compartment and in a tank to submerse for etching while we replace the chairs upholstery too and a third investment to powder coat or paint.

Looking for an easy and efficient process it would be great if we could just use a tank to remove the old paint and etch the aluminum in one step; have you heard of such process?

I found following information:

http://www.finishing.com/1200-1399/1318.shtml

1. Sand blast.remove every bit of Al Oxide this is the key to success
2. 1-2 layers of Zinc-Chromate primer.
3. powder coat (electrostatically) with pigmented powder of your choice.

Wangito.

Assuming that the chairs are all identical in size, try and place rubber or plastic piping on those areas that get damaged by other chairs when stacked....stuck on if you have to slit it first......or even heat shrink tubing as it is very thin and will fit in anywhere where you have an open loop......or rubber paint on top of the normal paint. Just a thought or two!!

Zinc chromate is the primer to use on Al ( it can be either green or yellow in color ) after treating with some type of etchant for prep. 40 yrs ago we used an industrial product called "METAL Prep" for aircraft applications.

I'd check for industrial finishes for aircraft.

You allready have ample info. on paint systems. What you seam to lack is s/b advise:The most common s/b mediam is "diamond shot". That's not for you. "Glass bead" is ideal for aluminum. Although you might be better off with a dipping tank full of organic stripper.

Good Luck

Assuming the chairs are worth investing money in, I would go to an industrial paint shop or an automotive painter and inquire about Imron or equivalent. Another option would be to have the chair parts powder coated. Either of these finishes will stand up much better than normal paints. They are, however , expensive and must be applied by professionals.

Why mess around with paint? Why not strip them down to the frames and send them out to be anodized and then reassemble?

A hard anodized finish should give you good environmental protection and not require any upkeep in the future.

Travis

Hello Rlequeria, we are a manufacture of 100% solids Polyurethane coatings that are used extensively on Aluminum ships and parts. The most important part of the coating process is the preparation of the surface. Sandblasting is the best as it will give the best profile to the surface, however, it is expensive and there are many types of abrasives you can use. We also use a hand power tool called a "Monti tool" see their web site, www.mbxit.com This tool give us a nice surface profile for parts and smaller areas that need coatings.

Our coatings are 100% solids and come in either brush/roller kits or spray kits for volume. The coating is called Specialty Polymer Coatings ( SP 1386) and if you need more information on it, please call or email me and I will be glad to send a sample for you to try.

778-231-6027

Norm@spc-net.com