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  View original topic: VHT Rattle Can On Cast Aluminum?
Vanapplebomb Thu Nov 06, 2014 6:18 am

I would like to paint my cast aluminum fan shroud. I have had good luck with their engine enamel on steel but I have never really done much paint over aluminum before. Is any prep work or primer necessary or can I jus shoot it with some VHT rattle can paint and bake?

Northof49 Thu Nov 06, 2014 9:19 am

I only have experience with the VHT satin black epoxy and it holds up extremely well on bare aluminum. I painted the forks of my three wheeler around 4 years ago with it and there isn't a scratch on it, despite driving through brush and weeds.

raygreenwood Fri Nov 07, 2014 8:36 am

Its worth a try. There are numerous threads on the STF from a while back with, different takes on painting/coating the shroud. The problem is the type 4 shroud is not just aluminum.....its an aluminum/magnesium alloy and does not take paint well. Ray

Mike Fisher Fri Nov 07, 2014 9:37 am

Tram painted all my new engine except the air cleaner with spray cans & I am happy to show it off now!

Vanapplebomb Mon Nov 10, 2014 8:45 am

I wonder if an epoxy primer would adhere well to it. I have seen several nice paint jobs on them, but never know what they did to get it that way.

Can you use one kind of primer, say an epoxy primer, and then paint over it with another kind of paint without messing up the primer base coat?

raygreenwood Mon Nov 10, 2014 9:12 am

Vanapplebomb wrote: I wonder if an epoxy primer would adhere well to it. I have seen several nice paint jobs on them, but never know what they did to get it that way.

Can you use one kind of primer, say an epoxy primer, and then paint over it with another kind of paint without messing up the primer base coat?


The real key that we have not seen enough of is.....yes....we have seen quite a few nice paint jobs on shrouds.....but how many have lasted and for how long? I have mot seen much long term report back on whether the paint is starting to flake off which is the most common issue.
maybe ....if there is not, one already. ...you, could start a painted shroud thread so people could post what they have done and how long it lasted. Ray

Mike Fisher Mon Nov 10, 2014 9:56 am

Aluminum/magnesium is ugly even when clean & only looks worse dirty! Painted it looks/cleans good. Primer would be good under the paint but it doesn't have to be epoxy. Use primer that best matches your paint.

jspbtown Mon Nov 10, 2014 1:26 pm

I am not a pro but I would think that a good, two part epoxy, would be able to stand up to just about anything from a rattle can.

raygreenwood Mon Nov 10, 2014 3:10 pm

Mike Fisher wrote: Aluminum/magnesium is ugly even when clean & only looks worse dirty! Painted it looks/cleans good. Primer would be good under the paint but it doesn't have to be epoxy. Use primer that best matches your paint.

Yes...agree....but the point is....with this manifold....is that about 90% fail to get ANYTHING to stick long term.

We can be sure its a combination of either cleaning/degreasing and/or proper paint mixture/type and/or poor application method/temperature/environment......but so many people who have used very good habits and methods with a wide range of paints and coatings.......that there is no clear reason (yet) for the failures of paint to stick to this part and material.

Its got a lot of heat expansion/flex and vibration......and its also very porous.

Let us know how long yours lasts.

I do look at it like this though.....if it lasts 3 years before it starts to crack and peel at all....and if it comes off easy.....thats fine with me. Its worth having my engine out about every other year anyway. Ray

Vanapplebomb Wed Nov 12, 2014 5:22 am

I just posted the question to the Bay Window Bus forum. Lots of painted blower housings in there. Guess I will see what kind of answers I get.

eyetzr Wed Nov 12, 2014 10:54 am

The issue with most of paint falling off & failure is bad prep. The problem with cast parts, mag. or al. is they are porous. These small cavities hold contaminates & then it gets warm & they try to escape & push the paint off. If you steam all the parts you want to paint & wiped them with wax & grease remover, you will see the oil trying to get out. I sand blasted my shroud & the next day wiped them for prime & they still had oil trying to get out. Ended up soaking the parts & hitting them with the compressed air.



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