Topic: hi-temp etching primer for aluminum

[mazingerzeca]

Hello all.
Before painting the engine cranckases, cylinders an cylinder head of my bike, I made a test on a tappet cover.
The piece was degreased, sanded, washed and cleaned with a solvent, and after that, painted with VHT Hi Temp engine enamel. 24 hours after painting it was cured on an oven at 200º for an hour.
Then, I scratched the piece with my (powerful) nails and the paint went off. Hope you can see the painting in my nail 
So, I hope I will have to use an etching primer for that paint, because I think that the problem is that is very difficult for the paint to adhere on aluminum. I've seen some posts about painting and some people uses an etching primer, but does the etching primer have to be hi-temp also?
I've seen some cans of Duplicolor Hi temp primer, but is not an etching primer. Given that the cranckcases were sandblasted some weeks ago, the primer should be etching.
Which primer do you use for engine paint? Any brands? Here, in Spain, we have access to Duplicolor products basically. I could not find Alumiprep 33 or POR-15 products. Any suggestions?
Thank you.

[.RJ]

I've used Duplicolor high-temp engine enamel with good success on lots of parts - even wheels.  It seems to take a few days to cure (maybe heat would help here) but after that its very tough.  I painted a set of hubs, and even after having a #$%* of a time getting the rear bearing retainer off the paint wouldnt scratch up.

[nippon]

Sorry to hear about your problems to get the VHT SP118 primer, but I took it from the ebay shop i told you.
If you like, I could start a request.
I'm fully satisfied with the result. About duplicolor, I heard that it will nost last very long and it would be
not oil and gas resistant. (take a search on the board).

You get the best results when you spray it in a very thin layer and from a distance of almost 10-15 inches.
I think it's worth to get the VHT primer and paint. It lasts, I do not have the problems you wrote about.
Good luck.

nippon

[mazingerzeca]

Thanks for the repplies.

Nippon:
I think that I could buy the primer from the e-bayer whom I bought the paint. The paint in your picture is the same I used, but I think it's necessary to use the primer.
Do you know if the primer contains something like "phosphate components"? I've read that it is necessary to etch the surface of the parts.

If the primer doesn't contain phosphates, maybe it will not adhere to the surface. Even if the pieces have been sandblasted, I know that if painting is not made inmediately, a light rust is formed on alluminum surface. In the picture you can see how the surface in which I am going to paint is. A half is sandblasted, but some time passed from it, and the other half has been sanded by hand to get off some scratches. I didn't give it a polished finish.
- Did you paint inmediately after sandblasting the crankcase? Did they have the same surface that mine have?
So, I think that these are not good surfaces for the painting to adhere. At this point, what should I do?
- Spray the primer over this surface and after the primer the VHT engine enamel? Will VHT primer adhere to a surface blasted a month ago?
- Do the sandblasting again and paint inmediately with primer and engine enamel? (the sandblasting costs was 200 euro)

Regards,
Ignacio.