TheSamba.com :: View topic - Fan Shroud(housing)

Sun Oct 16, 2011 6:13 pm

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:

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!

Sun Oct 16, 2011 6:23 pm

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.

Sun Oct 16, 2011 6:27 pm

Westfabulous wrote:

Oh sweet picture, that is very gold looking isnt it...

I have an earlier shroud on the bus right now, that i also cleaned meticulously. though that was a couple years ago now, i dont recall seeing the goldish or plated appearance.

I'm thinking that gold plated appearance looks good. i'm going to call some plating shops and see what they say about plating magnesium. i think it would look sweet in original plating....

Sun Oct 16, 2011 6:31 pm

rustbus wrote: I'm thinking that gold plated appearance looks good. i'm going to call some plating shops and see what they say about plating magnesium.

That's a fantastic idea. If you go ahead with this, please post the details for everyone to read. As for me, the governing factor would be going with what was original. Your shroud is a GD (seemingly gold); mine is a GE (very silver). If the shroud is the correct one for your bus, then I say go for it. Below is a picture that I borrowed from a thread. You can see that it appears to be all silver:

Sun Oct 16, 2011 6:45 pm

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

Sun Oct 16, 2011 6:59 pm

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!

Sun Oct 16, 2011 7:35 pm

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.

Sun Oct 16, 2011 7:53 pm

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.

Sun Oct 16, 2011 8:22 pm

Thanks Busdaddy

Sun Oct 16, 2011 8:29 pm

busdaddy wrote: 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.

hmm super interesting - and yeah i would love to batch up a ....batch but that sounds like a lot of volatiles for a single shroud...

what options are commercially available today that can recreate this type of finish? i see you can anodize mag but its a little specialized...not sure if we have that option here in my city...

i'll let you guys know what the locals have to offer. it surewould be nice to know what the alloy of these shrouds is - or are they 100% mag?

Sun Oct 16, 2011 8:52 pm

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

Sun Oct 16, 2011 9:14 pm

SGKent wrote: 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.

X2.....skip the greasy kid's stuff. Get a rattle can and go at 'er. Save the money, and the aggravation. 5 years from now it's going to need to be done again in all likelihood anyway.

I'm not suggesting for a second that Busadaddy's idea is a bad one, but at the end of the day, I would do the cost benefit analysis before I went down that road. If the project was a full blown mint resto, then maybe it's worth it. It certainly is handy to have options, and Busdaddy's resourceful recipes.

Quite honestly, I think that gold looks great, but to my eyes, the only thing that looks authentic to me is the natural patina. It looks real somehow. I also really liked the color that Curtis4085 used. I'd love to see a fan shroud that has been bead blasted and clear-coated. I bet that would look good.

Steve: How did you get that gold finish on your transmission? It looks good and it appears as though it was derived through some sort of chemical reaction.

Mon Oct 17, 2011 9:13 am

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.

Mon Oct 17, 2011 9:55 am

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.

Mon Oct 17, 2011 10:45 am

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"

Mon Oct 17, 2011 11:20 am

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?

Mon Oct 17, 2011 11:23 am

Check out Gibbs Brand. Works great on magnesium.

Mon Oct 17, 2011 1:06 pm

busdaddy wrote: 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?

Ha! I cleaned most my parts in the dish washerespecialy the plastic bits. Good idea, but make sure the miss is out :wink:

Whats the process Joe Ruiz (MrOkrasa) uses to coat old VW motors?

Mon Oct 17, 2011 2:34 pm

SGKent wrote: 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.

I love this look. It looks very authentic and real. If it was a durable product, I'd give it a try.

Mon Oct 17, 2011 4:28 pm

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