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Fri Apr 20, 2007 10:57 am

I recently cleaned the engine in my zwitter using walnut shells, now there are white oxidation spots, is there a coating that will stop this and still maintain the original luster & color?

Fri Apr 20, 2007 11:23 am

This is what I´ve learned while studying the subject: Original method used by VW in the early fifties for magnesium finishing is a dichromate treatment called "Dow chemical treatment nr 7". The Michigan company DOW was the main supplier of magnesium for VW in the early fifties according to one web source. The method is explained in DOW´s publication from 1955 called "Magnesium Finishing". The color of the finish of the NOS blocks I´ve seen is kind of light bronze and according to the book it varies from light to dark brown depending on the alloy. I have the book and I´ve tried to get some Europeans interested in starting the business but so far without success. Maybe somebody gets interested now? I have a couple of blocks and gear boxes that would like have an og coating.
b/r Heikki

Fri Apr 20, 2007 1:10 pm

I know the concours porsche guys are heavy into this. You might try asking over on their forum? There was a thread on this a while back (It was either here on thesamba or on kabriolett). I seem to remember something about the coating adding a dimensional thickness to the motor and throwing some of the machining accuracy off? I don't quite remember under what circumstances this was however.

Fri Apr 20, 2007 1:25 pm

Some Dow methods do but quote nr 7: the treatment effects no appreciable dimensional changes and normally is applied after machining. Castings and other parts containing bearings, studs and inserts of ...(different metals)... may be treated since these metals are not effected by treatment No. 7".
Heikki

Fri Apr 20, 2007 1:56 pm

Have you tried locating a copy of the Dow handbook on Magnesium Finishing ?

Fri Apr 20, 2007 2:45 pm

I have the book but I need to find a plating company that has all the equippment, experience and will to start the business. And obviously they need more customers than just me. This is one of the "don´t try it at home things". As I recall Dow stopped using the method due to environmental concerns.

Fri Apr 20, 2007 4:00 pm

Dow 1 or 20 work just as well. You can do both of these chemcal washs at home, no problem. All of them create a conversion coating and all are sort of the same bronzish, goldish, brownish color. It depends on your alloy. The best thing to do is to try it on a small part. No big deal you can take it right back off again. That property is why you almost never see it as it comes off so easy. I have been trying "tricks" to keep it on. That is the real secret to the process for show purposes.

Thu Apr 26, 2007 11:04 am

We have cases coated (chemical plating using heat & electricity) at several shops in Calif. and in Florida. You need to supply an absolutely clean case (near "white" metal) and they replate the case. It cures the production of "flour" on the case. You need to specify the darkness or shade of "gold", essentially. We use a NOS 36hp case as a base line. It is a labor intensive process.

Try SpeedwellUSA.com. They can give you a price for this.

(from the vintage speed drivers in No. Cal.)

Sat Apr 28, 2007 6:44 pm

It was a little expensive $350 if I recall but it does look a lot nicer than dingy gray.

-Craig

Sat Apr 28, 2007 7:13 pm

that process is called "electro color" here , it is a simple anodizing process.

it goes from light gold through brown to black , and depends on :

1: voltage applied
2: temperature aplied
3: ALLOY OF THE ENGINE

Sat Apr 28, 2007 7:14 pm

forgot , it is not expensive here , since it does not use any dyestuff to create the color , only heat and voltage , also , the block will have to be completely stripped and with no steel parts on it , otherwise it would ruin the anodizing solution

Sat Apr 28, 2007 10:01 pm

Gosh guys, just go google for DOW 1 or 20. All you need are simple chemicals from the chemical supply. A spotless case and you just use a paint brush to wash it on. Rinse with clear water. Done. No big deal. Just like factory.

Sun Apr 29, 2007 5:27 am

couldn`t find it at google .....this is dow`s web site , can you find it ??

http://www.dow.com/products_services/index.htm

Sun Apr 29, 2007 9:55 am

You have to be creative in your searches. Try:

DOW x conversion

where x is 1 or 7 or 17 or 20. All bring up stuff.

Example for DOW 20:

Dow 20 (Modified Chrome Pickle) was developed to
provide a more uniform colored coating than Dow 1.
Treatment 20 may be used on all magnesium alloys but
is particularly adapted for magnesium DIE castings.

Sodium Acid Fluoride 2 oz/gal,
Sodium Dichromate 24 oz/gal,
Aluminum Sulfate 1 1/3 oz/gal,
Nitric Acid (70% Nitric) 1 pint per gallons..

5 seconds to 2 minutes.

Sun Apr 29, 2007 11:19 am

I am looking for a company that can apply DOW 17.
Please PM me if you know of one.

Sun Apr 29, 2007 8:40 pm

Would this process have been used on a 1959 beetle? or just the early 50's beetles. I have the original 36 horse for my 59 and im very interested in treating the original case. Ive asked all the local automotive machine shops and noone knows what the heck im even talking about!

Mon Apr 30, 2007 3:18 am

if someone does it , post before and after pics , please :D

Sat May 05, 2007 1:35 pm

r39o wrote: You have to be creative in your searches. Try:

DOW x conversion

where x is 1 or 7 or 17 or 20. All bring up stuff.

Example for DOW 20:

Dow 20 (Modified Chrome Pickle) was developed to
provide a more uniform colored coating than Dow 1.
Treatment 20 may be used on all magnesium alloys but
is particularly adapted for magnesium DIE castings.

Sodium Acid Fluoride 2 oz/gal,
Sodium Dichromate 24 oz/gal,
Aluminum Sulfate 1 1/3 oz/gal,
Nitric Acid (70% Nitric) 1 pint per gallons..

5 seconds to 2 minutes.

So you just get these chemicals, mix them up, and brush it onto an immaculately clean case? Is it really that simple?

If I can source the stuff to do it I'll definately give it a shot.

Sat May 05, 2007 5:32 pm

You have to leave it on for some amount of time. Then you rinse it off with water. It is conversion coating. It isn't real thick. It almost can be rubbed off. But, it is what was applied to magnesium to keep it from oxidizing. Since it comes off easy, it is the reason you never see much of it on a part decades later.

Sun May 06, 2007 10:37 am

Would I have to mask off certain areas of the case, i.e. the oil pump hole and/or cylinder surfaces? Or is it OK for this stuff to get everywhere?