I am trying to finish my notes to accompany the rebuild video (notes will be free) and I am wanting to pick your collective brains for info on corrosion prevention for the mag alloy case. What do you do? The factory coating only lasted a few years and is long gone now. On most peoples cases, it is the oil that keeps it from corroding

The one sitting on my garage floor is coated in wd-40 and shows no corrosion after 4 years.

Nickel plating, a little bling bling....

I cover mine with 40 yr old German steel and don't look at it.

sacrifical anode?

I know one can clear coat a clean one. There is this stuff called "Gibbs" or something like that which some have tried with success. There is no shortage of people that will clean these things, but they do not know to coat it and they start to deteriorate.

MOTOR OIL and dirt works great!

I know, I mentioned that

I try to make sure at least one of my valve cover gaskets are leaking and maybe one other high level oil gasket is giving up a little oil all in the name of protecting my prized 901.

but seriously,


http://www.finishing.com/faqs/magnesium.html
Dow 17 surface conversion coating if it's Magnesium.

Is corrosion a serious issue? Rust on steel is a horrible cancer that destroys, but the transmissions don't really decay. Is this for purely cosmetic reasons?
Please forgive the dumb Qs, just wondering.
I've also seen people paint them... The pros and cons might be worth mentioning in the vid?

Can't wait to add the Evil DVD to my library!

I think this could apply to /6 fans too... aren't they magnesium?

Not like 914/6 guys ever see their fans, though.

Never bothered. I might want to at some point though (the six resto), so this thread is a bonus.

Mike,

I started a long term test of a few cleaning and protection methods a few years ago. Check this out...

http://motorsport.zyyz.com/project_914_03_14.htm

Last update was early 2008. Part is still hanging up outside and I need to bring it in and take some more photos. I look at it periodically, but in general I would stand by what I said last time I posted and that is...

* Media blasting is the best at cleaning, but it removes the chromate conversion that may still provide some corrosion protection.
* Gibbs Brand Penetrating Oil/Lubricant works, but it's not a miracle product.
* CRC Heavy Duty Corrosion Inhibitor seems to work the best. This is not surprising since Porsche also used a waxy protectant (Tectyl) on the magnesium transmissions parts.

So short of finding a place to buy Tectyl (what the factory used and I can't seem to find anyone who sells it in small quantities), I would go with "CRC Heavy Duty Corrosion Inhibitor".

http://www.crcindustries.com/ei/content/pr...N=06026&S=C

Occasionally I find this stuff at stores, but generally I have to order it. It is somewhat targeted at boaters, so I have yet to see if boating supply stores carry it on a regular basis.

Richard

I should also mention that I was looking to go for "period correct" look/style (I also wanted it to be cost effective) with respect to a method to protect the transmission case. Back in the day Porsche used a chromate finish to provide temporary protection to the parts between the time they were machined and when they were assembled. Chromate finish provides decent, but not long term protection. So it was never intended to really protect the case. What Porsche did was spray the assembled case with a product named Tectyl which is a waxy coating. The CRC product above is similar to Tectyl.

If you are not looking for period specific or a low cost solution, then there are many newer coatings (particularly aerospace based) that can be used on magnesium and aluminum. However some of those may result in oddly colored finishes (such as green). You might be able to find someone willing to do another chromate conversion process on a case if you want to replicate the factory finish (particularly the brassy color the chromate finish gives). However most (all?) chromate conversion processes use hexavalent chromium which is nasty stuff. The movie Erin Brockovich is about people who were poisoned by hexavalent chromium. So the stuff is just about outlawed today and may be expensive to have done.

I have not put much thought into painting a case and if that is a good idea for the long term. However I know that many people do paint their cases.

30 years of grease and gunk are keeping mine pristine underneath

I'm about to order something myself so this is a timely discussion. I got mighty frustrated last year trying to find Tectyl. But in addition to Richard's suggestion, which is described as "dark amber" have any of you tried CRC 3-36 product as well?

http://www.crcindustries.com/ei/content/pr...N=10200&S=Y

It's temperature range is up to 300 degrees and it's just plain "amber" which Tectyl is too. I don't know how that compares with the Marine CRC stuff. According to the spec-sheets, the marine stuff appears to be more viscous than 3-36. Here's a newer coating. I don't know anyone using it on one of our cars.

http://www.tagnite.com/video/ and

http://www.tagnite.com/

Links to Tectyl:

http://www.daubertchemical.com/main.taf?p=3,1

http://tectyl2.valvolineeurope.com/index.a...ba0e5105135c4d5

Also, here is a link to an old thread that covers a lot of ground on this topic.

http://forums.pelicanparts.com/porsche-911...-corrosion.html

Good reading!

Eastwood, Aluma blast spray.

Pelican was going to sell Tectyl, but ran into problems with shipping it I believe.
The CRC marine HD material seems to be the best alternative, but it is hard to find. It is possible that only marine stores can get it, our FLAPS cannot.
Gibbs brand lube is possibly the next best inhibitor.
Talking to local trans shops they just use a spray on lube like WD40.

I haven't heard of that CRC 3-36. I read that link and it sounds like a non-drying lubricant (much like Gibbs Brand). If anyone tries it out let me know how it works out.

I haven't tried to buy Tectyl in a few years. Everyone I could find was geared up to provide large quanties. Not to mention the fact that Tectyl is a brand name and not a single product. So you have to make sure you buy the right thing. That PP thread is great and it was the source of PP planning to sell Tectyl. Grady Clay had found a source for Tectyl 846 (which he said is what Porsche used). But for whatever reason (maybe shipping issues as Dave said) that fell apart.

I just Googled a few minutes ago and did find a supplier that apparently sells Tectyl 846 in spray cans. They list a case of 12 cans at $76 which I think is reasonable. So I ordered a case.

Here is the link if anyone else is looking for it...

http://www.mil-specproducts.com/productPage.aspx?prodID=446

I am guessing that there is not going to be a huge (if any) difference between the Tectyl 846 and the CRC product.

Got some exhaust spray from Chris last year that works really good and looks like metal. Wonder how that would work.

Redline Tranny Juice(no corrosion)

We are talking about exterior protection, unless you are suggesting you poor it on the outside?

If you are talking interior, just make sure it's the GL-5 version.

If you are talking interior, just make sure it's the GL-5 version.
[/quote]

That's what I've heard......never tried it!

I have no idea of the cost on this stuff but they say it's clear and dries to the touch.

http://www.socomor.com/englishFT/SOCOPAC%2...H_19176AGGB.pdf

I've used cosmoline type sprays in the aircraft industry. They work great but collect dirt like crazy. It also gets sticky when warm. We would clean all the dirty stuff off every C check and then re-apply.

HPC S02

From my mag casting days, the magnesium institute book recommends zinch chromate paint. The zinc acts as a sacrificial anode to prevent corrosion, and the binder in the paint seals and protects. Comes in green and bright yellow.

My tranny has a thin coat of aircraft grade zinc chromate paint on it, and a thin coat of wheel silver.

My second choice would be the tan tectyl like wax coating suggested by the factory. Some of those coatings have corrosion protectants formulated within.

For those of you that passionately believe that paint prevents appropriate cooling, you might research the heat transfer rate through the factory recommended tectyl like coating, or the heat transfer rate through the usual coat of grease, oil, and crud.

Bottom line, uncoated it rusts, and appropriately coated, it won't.

Click to view attachment

Aluma blast: Eastwood

VHT high-temp clear

Click to view attachment

Paint is another option 30-40 years out - from my tranny soda blast topic's post:

After blasting or cleaning - you may want to try a clear coat HT engine or exhaust paint like those here from VHT (or another paint/coatings mfgr.) to seal in the Magnesium alloy case material.

http://www.vhtpaint.com/flameproof.html
http://www.vhtpaint.com/engineenamel.html

They also have a magnesium metallic if your case is really badly stained into the metal.

In all cases - proper surface prep is a must to have adherence, & check each paint to make sure it's made to stick to the specific alloy on which your applying.

The other coatings & protectants will work well on a case that's in good condition (under the usual crud), but more damage &/or corrosion may require a paint job.

GREAT info guys!

Ken - from your mag casting days - what's the best way to remove the zinc chromate safely (green if it matters)??

I got a set of 5 used Fuchs 2L Alloys which a DAPO had primed with Z-C then painted Phoenix Red for the LE look I suppose (or had it done). They are in very good condition under the paint/Z-C - that having protected it all these years, but I wanted to remove the paint & Z-C before I take them to Al Reed for a full-on resto & re-anodizing. I've tried Acetone & a rag, but it's painfully slow & may score the surface (as did the seller with a soft toothbrush & rag - BTW he was not the DAPO).

Any suggestions for materials & methods to safely, more efficiently & effectively remove Z-C?

Not to hijack your thread Dr. E - but removal would be the same for paint &/or Z-C on the transaxle cases too - so it's really applicable here too!

When working with new parts, you apply coatings, not remove them.

That being said, paint stripper would be a good guess. Not sure what is in each brand, bit I would stay away from acids and bases (lye). Test on a small area to see if it damages the anodize.

Wood scrapers with angled tips are easy to make, softer than the aluminum, and do a fair job scraping softened crud.

Dry ice blasting can definitely strip them because it is used to strip airplanes one paint layer at a time.

Not sure if soda blasting is OK.

I'm reviving this thread because I've just bought CRC SP-400.

http://www.crcindustries.com/ei/content/pr...N=03282&S=Y

It's a better solution than the CRC 5-56 I mentioned early in it. I'll post when I get finished coating both a 914 and 915 case and give a followup in the spring after a winter full of water and... stuff.

Fortunately Arkansas uses more dirt than salt. The SP-400 seems very close to Tectyl both in consistency and color and has a working temp of up to 300F.

Should be ok certainly in the winter, and track temps with a clutch/LSD should be ok as well with a trans-cooler shedding BTU's

I have a 1949 Allis Chalmers tractor with some original paint on it. Unfortunately it is lead based.
Why not media blast then prime and paint with a product like PPG Omni.
Or polyurethane primer in a rattle can. The local Sandblaster uses it.

I'm reviving this old thread to provide an update. You can now buy small quantities of Tectyl 846 through Amazon: https://www.amazon.com/gp/product/B00HUY9UG...=UTF8&psc=1

I've used it on both my engine and transmission case. Just did the transmission yesterday. here is a pic.

You can buy direct from the manufacturer. Larger quantity, less money and free shipping.

https://petroleumservicecompany.com/tectyl-846-class-i-2/

Every time I opened a painted trans it was a crappy "rebuilt"

Yea. The Krylon “rebuild” exists even in the Porsche world.

Has anyone tried T-9?

Yes. Seems to be good stuff. I used it on my fan shroud and so far it has stayed a nice factory gray look so far (about 2 years indoors). I also treated my transmission case above with it a week before daubing on the Tectyl. I think the Tectyl will provide significantly more protection, but the T-9 is invisible and doesn't leave a waxy coating if you want to avoid it.

I used LPS 3. Leaves a waxy coating.

What was used to clean it and did it need to be gutted?

I was going to spray mine with Gibbs, but forgot to and now it looks not-so-great...I guess I can clean it and spray.

I have been second guessing not putting a TB Diff in it (no need for LSD since it'll be street driven) when it was rebuilt. Since it's still out I might revisit that idea. hmmmmm

Try spraying with Gibbs anyway, or try a small section. It might bring back the finish. Couldn't hurt in the meantime

Good point, worth a shot right My shiny billet side and intermediate plates really make the dull/dark case stand out. Let me try it and I'll post a photo when I do

Like Boeshield T-9?

I can't believe I never thought about using it. Works great on my table saw and jointer.

And I can't believe I never thought about using it on my table saw!

I just cleaned mine really good and painted.....If it come's off I'll touch up. Not a perfect solution but a stop-gap. MarkClick to view attachment

@bbrock

Light coat, buff off, then your favorite paste wax. Works wonders. My equipment is in an unheated garage which gets warmed up just for use in the winter so condensation is always an issue and since using T-9 I've stopped having table rust issues.

Edit: Make sure its really clean and relatively warm first so the propellant can evaporate in a timely fashion-or I've seen it get a bit gummy.

@jd74914
I've just been using paste wax. Of course that works fine but the instant indicator of when it wears is flash rust even in my low humidity world. Will be great to have that extra layer of protection soaked into the pores. Thanks for the tip!

When I started doing work for The Revs Institute the first thing I learned was how they relied on Boeshield to keep parts from oxidizing without coating them. Since I built the first engine for them I have been using it on every engine case. It doesn't smell, doesn't drip off, and it doesn't attract dust/ dirt as long as its applied in a proper amount.

Thanks Jake, that looks like a great product. Best, Mark