Fan Shroud(housing) - original finish?(gold) (Type 4)

rustbus

I've been wondering how to refinish my fan shroud... lots of reading on the various coating guys have applied, but not a lot of discussion about what was factory.

in this thread ( http://www.thesamba.com/vw/forum/viewtopic.php?t=100298&highlight=shroud ) ratwell suggests the fan shroud was "silvery" in color. he also suggests that sandblasting and clearcoating you would achieve the original finish...but i gotta disagree.

I'm thinking the original shroud was plated, like nickle or cad or something. after cleaning up my shroud, it has that goldish/gassy appearance:

Image may have been reduced in size. Click image to view fullscreen.

seems the exposed surfaces fade away first, this shroud was super greasy underneath so it was marginally preserved. on the back where it was greasiest its quite well preserved

maybe they starter plating later on? were they all plated? what would you guys say was the original process? sure looks nickle to me!
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May of '72 Deluxe. Red Bay Bus

2.0L L-Jet CS & 091 trans conversion
my Bus thread

Westfabulous · Posted: Sun Oct 16, 2011 6:23 pm Post subject:

Very good question, and I've wondered that myself. My shroud is original and hasn't been monkeyed with. It still has an old clearcoat-ish type of material on it (although worn) and the shroud seems silver through and through. On the other hand, the '78 and '79 brochure shows this (below). I've concluded that they came both ways, but who really knows? I know that everything else in my bus that had the gold anodized finish on it is still gold, so it doesn't make sense that just the shroud would fade. I also got a bunch of ancient photos from the original owner of my bus, and one had the engine compartment open (surprise, surprise). Although the shot was taken from about 30 feet away, the shroud appeared to be silver, even 30 years ago.

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rustbus · Posted: Sun Oct 16, 2011 6:27 pm Post subject:

Westfabulous · Posted: Sun Oct 16, 2011 6:31 pm Post subject:

skills@eurocarsplus · Posted: Sun Oct 16, 2011 6:45 pm Post subject:

fwiw, working for volvo for the past too many years, all of the cars had a cosmoline type sealant on the engine, which is all aluminum. it too has a goldish coloring, but will wear down/flake off over time. next time i see an older I 5 i will snap a picture. it looks alot like what is in the brochure
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Alex6373 · Posted: Sun Oct 16, 2011 6:59 pm Post subject:

The casting of the fan shroud was (my guess ) coated with a clear type of primer then the top coat of clear was applied . Due to the area, if not primed the single coat would have not lasted 40 plus years one coat to adhere to the fan shroud material and seal it from air to stop corrosion and a top coat to make it shine and make it somewhat cleanable . Over the years of usage some areas of the coating have failed and this could allow a colour change, even as it is being cooled with air temps can be quite high causing change.

Sorry I just blasted mine in Langley and rattle can it!

Wildthings · Samba Member Joined: March 13, 2005 Posts: 50348

The NOS T127 industrial engine I picked up definitely just had bare metal. I pulled the fan shroud off and set it aside and lacking even the nice oily coat most engines quickly acquire it corroded pretty quickly.

busdaddy · Posted: Sun Oct 16, 2011 7:53 pm Post subject:

The goldish coating is chrome pickle, it's a conversion coating used on magnesium parts. It's applied by soaking the part in a bath of chromic acid and a few other chemicals, it converts the outer few microns of the part to an inert oxide that resists corrosion better than bare mag and allows paint to adhere.
We used to use it on helicopter parts but AFAIK most of it's components are now banned or tightly controlled by the enviro zealots and workplace health babysitters.
I've got the recipe somewhere if anyone wants to attempt whipping up a batch.
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Alex6373 · Posted: Sun Oct 16, 2011 8:22 pm Post subject:

Thanks Busdaddy

rustbus · Posted: Sun Oct 16, 2011 8:29 pm Post subject:

SGKent · Posted: Sun Oct 16, 2011 8:52 pm Post subject:

I am not a plating specialist but I do know that some of the chromium compounds generated in chroming are cancer causing and that is why it highly regulated. Some of the places that were used for chroming are now superfund sites. A rattle can brass colored gold might be a safer product to work with that would approximate the finish. Or perhaps a goldish brown colored powder coat.

http://www.latimes.com/news/science/environment/la...ronment%29
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Westfabulous · Posted: Sun Oct 16, 2011 9:14 pm Post subject:

nathansnathan · Samba Member Joined: April 14, 2008 Posts: 1671

From the thread on shoptalkforums on painting the fan shroud, it's been established that paint is not going to stick very long to the magnesium.

This link is to some testing and info that Richard Castro who did the 914wiki did on a magnesium transmission part.
http://motorsport.zyyz.com/project_914_03_14.htm

I've blasted both sides (now) of this shroud with glass, and I was thinking of using CRC Heavy Duty Corrosion Inhibitor, rubbing it on with a rag. It's similar to the 'tectyl' coating that porsche used on transmission cases he talks about, though I'm not sure if they used this in addition to the chromate treatment on the fan shrouds.

SGKent · Posted: Mon Oct 17, 2011 9:55 am Post subject:

the transmission was cleaned then sprayed with CRC heavy duty corrosion control. I used aluminum paint on the shroud and it is holding just fine.I don't epxect it to last 100,000 miles but when it gets bad I will do it again - or maybe sooner with a color closer to original or a powder coat.

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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

rustbus · Posted: Mon Oct 17, 2011 10:45 am Post subject:

well, i almost lost hope!

calling the plating outfits in town, non of them can help. most deal with electroplating so that rules out mag.

called the anodizing place i used previously. they do Chromate conversion coating, and with the goldish hue as well (clear is available, but they dont do it, their customers prefer the gold).

issues - preparation is key for final appearance. says to stay away from media blasting, use fine glass bead at the most or ideally soda blast. (i will try my homemade soda blaster and see) media particles get stuck into the porous surface and look bad after the finish is applied. its also hard to be uniform.

getting the remaining chromate off is the biggest issue, they only chemically strip at their facility so they would wager to say it would come out blotchy.

they have little experience with Magnesium but since this is not an electrical process, he says it will either adhere or not, very little chance for physical damage to the part. he cant see why not, biggest issue is that the alloy varies and nobody every really knows what it is.

its a $60 minimum, which this would fall into. i'm going to think about it and see what my homemade soda blaster can do to the leftover coating. it its too much labour, i'll probably just clean it up and clear coat it or just leave it be. i am also considering using another spare shroud as a guinea pig.

Edit - they refer to it as "alodine"
_________________
May of '72 Deluxe. Red Bay Bus

2.0L L-Jet CS & 091 trans conversion
my Bus thread

busdaddy · Posted: Mon Oct 17, 2011 11:20 am Post subject:

Alodine is for aluminum but may sort of work on mag or at least a mag/al alloy, I was going to dig out some of mine and try it but haven't had a chance.

Get yourself a bottle and do some experimenting: http://www.aircraftspruce.com/catalog/cspages/alodine1201.php As for pre cleaning most recommend an alkaline bath IIRC, think a shroud would fit in your dishwasher?
_________________
Rust NEVER sleeps and stock never goes out of style.

Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
Stop dead photo links! Post your photos to The Samba Gallery!

Слава Україні!

Hoody · Samba Member Joined: November 28, 2007 Posts: 1948

Check out Gibbs Brand. Works great on magnesium.

notchboy · Posted: Mon Oct 17, 2011 1:06 pm Post subject:

Westfabulous · Posted: Mon Oct 17, 2011 2:34 pm Post subject:

raygreenwood · Posted: Mon Oct 17, 2011 4:28 pm Post subject:

Busdaddy is spot on. Here is the process you are looking for. It can be more involved and nasty than you think.
http://www.finishing.com/faqs/magnesium.html

Be aware,,,you are going to need chromic acid (sulphuric acid and dichromate mixture and chromium trioxide). Some of the byproducts are Chrome 6 (hexavalent chrome)....which is highly highly carcinogenic. Ray


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Fan Shroud(housing) - original finish?(gold) (Type 4)
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