17prospective buyer

I have a buddy who works on a powder coating line. He can do my intake and cam cover pieces for free, but i have to have them ready to go. So, i need to get them blasted professionally then primed with something suitable. The primer logically should be compatible with:

-high temps of powder coating process
-not react with the mag/aluminum alloy
-protect the mag/aluminum alloy from oxidation
-be compatible with the type of powder particles used in powder coating/be a suitable substrate for powder coating

I went to the local auto parts place and asked the guy for a suitable primer for the magnesium/aluminum alloy, i stressed the fact that it was mag/aluminum and therefore unique. He recommended just self etching primer. So, i bought Spray Max 1K Self Etch Primer Filler thinking it would be suitable for use right after i got the pieces blasted. Now i'm not so sure however.

Upon reading the technical information sheet about the stuff, it says "Do not coat with polyester and EP products." I also searched for a max temperature rating on the PDF sheets and couldn't find anything for that.

What does the powder used in PC consist of?

I want the pieces to be idiot proof to the powder coater, i'm not expecting him to pay much heed to the "mag/aluminum" thing seeing as he's doing it for free. So i'm going to do the offgassing, masking, and priming myself. He said they do not use offgassing, but do run pieces through a wash (i guess they do not need to offgas since the company is more of an industrial operation that deals with brand new metal, and not individual pieces).

What is a suitable primer for my above listed requirements?

BPG_Austin

No suitable primer for underneath PC that I know of. There are a few PC primers that would be better suited. Red Oxide is THE BEST for underneath cast Mag parts. Its shot hot and acts as a sealer. Any 'regular' primer, paint or PC will still allow offgassing bubbles through when the parts are brought to temp. Wouldnt' do you any good.
I'd clean the parts and hand them off to your coater. I'd also be very suprised if he would even consider coating over a sprayed primer. There are specific steps to shooting RO primer, and your guy needs to be aware of them. Doesn't shoot like regular PC. The added step of shootin RO, then base takes a lot of time. I'd buy your buddy lots of extra beer.

17prospective buyer

Spraying different powders isn't an option here, it's more of an assembly line and pretty much what you see is what you get, little room for custom options since the guy is technically not supposed to be powder coating personal items.

So how do i protect the alloy from oxidation? The main reason i asked about a suitable primer was because i don't know how long the parts are going to sit before they get powder coated and i know these parts oxidize so quickly. What about a zinc chromate primer? I have heard that would be suitable for powder coating over.

Ducman82

i have never heard of PC primer. the items need to be blasted THEN coated asap to be safe. it really boils down to home much a "Free" job is worth to you.

17prospective buyer

Ugh, maybe i'll give them a few bucks to just do it there then PC it if that's what's needed.

Ducman82

id recommend it. make sure the jobs done to spec. could not hurt.

Mrmerlin

blast the parts,
clean them with a good degreaser ,
then bake in the oven ,
then PC them.
No primers just the PC coating
Make sure to wash any parts that have been PC in hot soapy water prior to installing them,
there have been more than a few who have had engines seize due to blasting media coming loose after PC was done only to take out the cylinders

Lizard928

Pre bake the parts at 450 deg for 1 hour to off gas them. Or you will get lots of off gassing during and it will look horrible.

17prospective buyer

Perfect, thanks Colin!

But where do i find those silicone plugs and caps Ed Scherer was talking about in his writeup?

Rob Edwards

http://www.ebay.com/sch/i.html?_trks...ating&_sacat=0

17prospective buyer

Sweet thanks.

Lizard928

17PB,

what intake/valve covers? S4 or 85/86?

I have a number of intake and valve cover sets here and have a great PC that I work with.
Prices vary based on what colour its getting, but think $350-450 for intake valve covers, throttle quadrant, intake and valve cover washers, and water bridge. Seeing as how you're in Canada I could have a set coated and then just exchange yours for recoated ones. If you want to go this way a core charge would be levied to ensure I get your old ones back!

illini-heel

You need to degrease prior to blasting. The media should not leave any residue. The next step would be applying a pretreatment designed for Aluminum (such as Henkel's Alodine product line). After that, any epoxy or polyurethane prime will be fine with the powder top coat (those are PCIS, polyurethane blends).

One of the previous posters is correct in that it is recommended that you paint as soon as possible after priming (after 10-30 minutes of flash time) to reduce the risk of intercoat adhesion failure. If there is any sort of a delay (hours/ days) make sure to do a "water break" test prior to painting. Your buddy should know how to do this.

Also, the cure is determined by the substrate temperature, not the oven temp. What this means is that your part will over-bake if left in for the same cycle time as steel components.

To answer a couple of other posters, yes there is powder primer available, but if they are not set up to use it (it must be gelled in an IR oven prior to top coat), traditonal liquid primer is required (again, ONLY epoxy or p/u are acceptable)

illini-heel

Cursed smartphone input cuts posts.

I've been in Paint Engineering for over 20 years, so this isn't the first time that I've dealt with painting aluminum alloy in a powder system. Primer is must, however, as direct-to-metal powder coatings all shrink in the oven and leave exposed edges that provide entry points for corrosion and peeling. It is for this reason that DTM powder fares very poorly in cyclical corrosion testing.

17prospective buyer

Hmmm... this is getting more complicated than i though. Maybe i should just paint them... Lizard maybe that would be good. I have an 87 S4, so yeah the S4 ones. Color scheme i'm thinking is black intake and side covers, and red oil filler neck, red cam covers, red water bridge and coolant pipe fixture. What kind of finish would red be? I was hoping to achieve a medium-fine wrinkle finish.

Illini, thanks for posting. This is getting to be over my head if i have off these parts to a guy who is doing it for free. He'll probably just treat them like the parts he does regularly. So aluminum/magnesium would be baked for a shorter period of time to cure than ferrous metal like steel?

This is sounding like a bad idea now...