We'd like to begin making aluminum letters on our router. Does anyone have any tips on how to prep and paint bare aluminum?
Thanks, Al
Posted by Preston McCall (Member # 351) on :
Best way is to acid etch them with any aluminum etch from the auto parts store. You mix the stuff with water in a pail and dip the letters in. Wear safety gloves and do not breath the fumes. Mostly hydrogen...better do it outside.
Then use Sherwin Williams Zinc Chromate (oil based) primer. It is a dirty yellow color, compared to tohers out there that are bright green. Scuff and then you are good to go with a finish enamel.
I painted an aluminum panel this way 24 years ago for a sign that was outside untioll last year, when I rescued it and brought it home. The paint still is sticking. I did use hardener in the Lettering enamel from Martin Senour.
Lotta work for a permanent solution, but it pays to see your work hold up decades later.
Posted by Si Allen (Member # 420) on :
After all your fabrication steps...degrease the aluminum and apply etching primer that corresponds with the paint that you will be using.
Most automotive paint stores will carry everything that you need.
I gotta learn to use spel chek.
[ February 04, 2010, 09:00 PM: Message edited by: Si Allen ]
Posted by Brian Stoddard (Member # 39) on :
For medium to large projects I spray Matthews Metal pretreatment - 74 734SP. Great stuff, dries very quick.
We use the same method Si suggested. Simple and effective. We give the surface a sanding with a random orbit sander as the last step in fabrication before degreasing. We've quit routing aluminum on our router (except for Dibond). What with the coolant fluid and the fact you can't use your dust pickup system when routering aluminum, it creats such a bloody mess. We buy finished letters from Gemini. We've crunched the numbers, and it just isn't worth it for us to do them in-house.
Posted by bruce ward (Member # 1289) on :
raw aluminum, acid etch, zinc primer PPG, and the 2 part epoxy on that THEN topcoat....its a pain and I hate doin it and I gotta agree with duncan buy them outright if you can
Posted by Gregg Parkes (Member # 7710) on :
Si... that's speel chekk
Posted by Pete Payne (Member # 344) on :
if it's something gemini can't handle, save yourself a ton of work, materials and fumes and find a good powder coater, we use dynamic fx in Goderich, cheap, good and i don't have to do it! He used to own a signshop, then smartened up!!!!!
Posted by Pete Payne (Member # 344) on :
forgot to mention, great colour selection and some very nice candies/ metallics and special effect stuff too
Posted by Brad Ferguson (Member # 33) on :
Our process is similar.
I take one extra step. I do a degreasing wash both before AND after sanding the bare aluminum. Sometime surface contaminants can be ground into the aluminum by the sanding itself, so I wash the surface with lacquer thinner first, then DA sand with 150 grit, then wash again.
Our primer is an acid wash, self-etching one made by Matthews called PT Filler. You add the activator just before spraying. The activator contains phosphoric acid. Spray it nice and wet to give the acid time to bite. Then topcoat with polyurethane.
Most automotive paint makers offer a self-etching primer that is similar. A two-stage epoxy would be my second choice. Some of the self-etching primers are not recommended over previously painted aluminum, in which case an epoxy primer would be my first choice.
