I've acquired a small custom paint project on some aluminum. It's been years since I've painted aluminum and wanted to double check what I remember to be the correct process. Ive already stripped the old paint work and have the surface scuffed with red scotch brite. I THINK I used to mix up water and white vinegar 3:1, wiped the surface down, rinsed with water, a couple light coats of self etching primer (I used SEM aerosol, small projects), then top coat urethane. Does this sound right? I'm deathly afraid of adhesion issues...
should be fine...never heard of the vinegar and water thing, though...I usually 180 or 320 depending if I'm gonna prime or not, degrease, and use Variprime..
They sell green zinc oxide in a spray can at most aircraft & pilot supply stores. Check your local private aviation airport or go online and search for Aircraft Spruce.
None. EPA banned it. Like R12 to R134A, the old stocks have gone way up in price and, once gone, they're gone. Supposed to be some new "safe" equivalent. Never used it myself.
Your local paint supply house will have everything you need for making paint adhere to aluminum. When I worked as a sign fabricator, the painter would sand down the aluminum signs, wipe them clean until no traces were left on his towel. Then he'd use some sort of an etching solution, and a special primer. Then regular paint was sprayed over that. His entire painting department was supplied by a local paint dealer that carried everything from industrial applications, home, interior, exterior, automotive, etc. If I remember right, the paints were from Matthews, a PPG brand.
I would wipe er down good with a wax and grease remover you can pick up at almost any parts store these days on the cheap , I would be a little nervous about the vinegar leaving a residue behind witch would cause adhesion issues , You will be fine with that etch prime , but if you want great adhesion let it dry real good and give it one more quick and light scuff with your scotch brite , then tac and spray ...
What hasn't been mentioned is using phosphoric acid instead of vinegar, then following with chromic acid conversion coating. These steps aren't 100% required, but are standard practice used by industry, aircraft builders, and on aluminum car bodies. If your job is important it's worth doing. Depending on who is selling it, the phosphoric acid may be called Alumiprep, Aluminum Etch, Aluminum cleaner, etc. The chromic acid treatment has names like Alodine, aluminum conditioner, and aluminum conversion coating. Be sure to follow the directions with the products. Auto paint stores can get both of these products for you. Etching primer contains a small amount of phosphoric. It can help, but it's not a subs***ute for good prep and cleaning. Properly done, the two steps I described eliminate the advantages of etching, primer, but it can still be used without causing a problem.
XIM primer,,amazing stuff,you can find it at your local hardware store bonds paint to ferrous and non ferrous metals. HRP
right on, all great procedures, the only thing you might want to do is read the label to check and see if the particular etch primer you use can be topcoated directly with urethane or if you have to put a sealer down first, some etch primers you can topcoat with paint and some you can't.
I am not a big fan of "rattle can" paint but must tell you about a product I discovered about a year ago. I have been working on my current project and needed self etching primer for the bare metal. I saw a can of Rust-oleum self etching primer at Auto Zone. I bought a can and have been using it ever since. This stuff has great adhesion properties and the viscosity of it out of the can is pretty heavy. Looks very much like the Dupont zinc-oxide I use to buy by the quart which is extremely expensive now. Take the $7 chance and try this stuff I think you will be pleased. It is actually sold at select Harbor Freight stores and is currently on sale for $4.89 a can. A single rattle can goes a long way.
I build aluminum frame garden windows and my process is to clean with ZEP Purple Industrial cleaner, blow dry, Prime with Sherwin Williams P60 G2 wash primer. It is phosporic acid based and adheres very well. Top coat is common Sherwin Williams quick dry enamel. Never had any window flake the paint. Even when installed in a western side with hot Texas sun baking it all day.
Have had really good results with Alumaprep 33, and then prime immediately after cleaning, before oxidizing begins. Have never had adhesion problems with this proceedure. Most paint suppliers should have the Alumaprep.
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