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#1 jarm691

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Posted 25 January 2020 - 02:20 PM

I am currently having a 998 rebuilt and tuned up. The guy doing it is going to have the aluminium clutch housing and diff housing etc aqua blasted to bring them up nice. Is there any technical reason I cannot then have them anodised either silver or clear to prevent them re oxidising?



#2 alex-95

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Posted 25 January 2020 - 03:41 PM

I don't think it will anodise or not very well as it's cast and isn't just aluminium, it has other metals etc in it that won't anodise.



#3 jarm691

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Posted 25 January 2020 - 04:38 PM

Right. What do you reckon the best anti corrosion treatment is then?

#4 I hate Brian

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Posted 25 January 2020 - 04:43 PM

Clear lacquer 



#5 cal844

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Posted 25 January 2020 - 05:05 PM

2k silver paint then 2k lacquer, done this on one of my rocker covers and it's still holding up well.

#6 bpirie1000

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Posted 29 January 2020 - 07:20 PM

Large helping of elbow grease added frequently..
Unfortunately..

Edited by bpirie1000, 29 January 2020 - 07:21 PM.


#7 AP2020

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Posted 30 January 2020 - 02:27 AM

I am currently having a 998 rebuilt and tuned up. The guy doing it is going to have the aluminium clutch housing and diff housing etc aqua blasted to bring them up nice. Is there any technical reason I cannot then have them anodised either silver or clear to prevent them re oxidising?

 

As these parts are cast, they contain far too much silicon to allow a good anodising finish... 

 

https://www.ebay.co....tm/283570197476



#8 jarm691

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Posted 30 January 2020 - 10:32 PM

Yes i have done some research and realise that now. Once they come back from vapour blasting I may just 2k lacquer them.



#9 cal844

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Posted 30 January 2020 - 11:09 PM

Paint it with a silver paint then lacquer them

#10 bluedragon

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Posted 31 January 2020 - 06:47 AM

If you're farming out this work, I'd go with powdercoating (either a nice silver that you like or clear.) That will be the most durable and tough finish, resistant to heat, oil, and fluids.

 

The 2nd option is painting or clear coat. If done by a professional, they should know and be able to explain how they prep the aluminum for painting (vital for adhesion - clean aluminum almost instantly forms an aluminum oxide layer on top that is not great at sticking to paint. A aluminum prep/pre-treatment product is important to get a good bond between the paint and metal.

 

Even a 2K clear coat runs the risk of yellowing, especially if used in a race or daily driver environment. A polyurethane clear coat is the best type practical (as used on commercial airplanes and buses.) These are "high solids" coatings that are very viscous and heavy compared to conventional automotive paints. These are harder to spray by comparison, more prone to drips and runs, though on a transmission case this probably isn't a big deal.

 

They require isocyanate hardeners that are very dangerous to spray however without protective gear, so for most a professional is the best option to apply these. They are the toughest, most durable paints available.

 

A final option would be to use a moisture-cured urethane like POR-15 "Glisten Coat" which can be applied with brush. I've heard good things about this, but some negatives too. But it could be done at home.

 

For people that didn't do a vapor blast, remember it can have decades of grease and oil embedded in the pores of the aluminum casting. One way to get rid of this stuff is to bake it in an oven for a while to burn all that gunk out.

 

Personally, I might just opt for a good metallic silver 2K or polyurethane paint. Unpolished cast aluminum doesn't look that great clear coated, the paint may well look as good or better than the raw AL, and the pores in the AL will be sealed by the paint. Just make sure the AL prep is done before applying paint.

 

 

 

Dave



#11 jarm691

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Posted 31 January 2020 - 09:09 AM

What about having the ally polished Dave, then sealed?



#12 bluedragon

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Posted 02 February 2020 - 02:51 PM

I'm not sure that a sealant would last long in the conditions found underhood. With oil and fluid leaks, high temps, and other harsh elements it's hard to see any sealant lasting more than a few months. It would seem to me to be a tough task to re-apply the sealant in the tight confines of the engine bay. If you don't mind that, it's an option.

 

If you want that polished look, then a really good clear coat would be the way I would go. It's what wheel manufacturers apply to factory polished wheels. The trick will be finding someone who will clearcoat polished aluminum and stand by their work. Doing it right is tricky (the secret being the AL prep as I wrote before, even more so for highly polished AL due to the need to retain the brilliant shine.

 

Someone who can clearcoat polished AL wheels would be a place to look for this kind of work. Also, some of the powder coat colors look very much like polished aluminum (check out the "hyper silver" shades.) On a cast AL part, it might be hard to tell the difference between polished and a hyper silver powdercoat (especially if the aluminium casting is not very dense and has a bit of a pebbly surface texture. Sometimes even cast wheels don't polish up well because the casting is porous and not dense enough to polish up well.)

 

 

Dave







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