What finish on these magnesium manifolds?

[304065]

I spoke with Harry Bieker today and inquired as to what the early Weber manifolds were made from. "Magnesium," he said, "even as far back as your '66." I was somewhat incredulous, thinking they were aluminum, plated with Zinc or something. But he invited me to scrape the metal and see whether it produced very bright shavings (mag) or the duller Aluminum. He was exactly right, the manifolds are Magnesium. I knew the later black ones were mag, but this confirms it for the early ones too. And they are VERY light compared to the equivalent volume of aluminum.

So what finish is on them? It's like "Iridite" but not quite. Notice a couple things: the color of the finish UNDER where the bracket that holds the crossbar linkage mounts. Silver. Now look at where the castings were machined-- dull finish, almost like they were finished when they came out of the mold, and then the casting was machined and the finish removed by the grinder.

Does anyone know what finish this originally was? Many thanks in advance for any assistance.

[304065]

From one source: Ferric nitrate is also called Dow #21.

Ferric nitrate pickle treatments
This method has a mild etching action on magnesium and produces a bright or a semi-bright silvery surface. The treatment can be used as a base for clean organic coatings or for stand-alone protection against oxidation and tarnishing of parts during indoor shelf storage. Using this pickle produces a passive surface that increases the adhesion and corrosion protection of the clear coating. It also serves to prevent blemishes, such as spotting, blooming, and worm tracking in the coating, after it has dried. The controlled mild etching action of the solution also makes a useful cleaning pickle in conjunction with other chemical treatments.

[jpnovak]

I only know that my weber manifolds have a really tough paint. I assume its epoxy based. Its really hard to get off when you want to repaint or powdercoat.

So Ferric Nitrate would work well on cooling fans and their housings? What about valve covers, chain case covers, etc? Interesting...

[304065]

Jamie, that paint was used on the later manifolds, it's a semi-gloss black. Harry Bieker believes it's DuPont Imron. He claims that it's VERY hard to blast off because the glass beads bounce off due to the fact that it's not very hard.

I wouldn't jump to the conclusion that Ferric Nitrate is correct, I only threw it out there to see if anyone recognized it. Ferric Nitrate is also known as the "Dow 21" process. Of all the chemical processes I have researched, it's one of the only ones that gives a bright silver finish. Iridite and Alodine do a dull brown or gold color. Dow 7 is brown.

Ferric Nitrate just about meets every definition of Hazardous Material I can think of except radioactive emissions-- for sure I'm not doing it myself. I've reached out to a couple of metal finishing companies but haven't heard anything back yet.

[304065]

Update for those who have been following the manifold color question.

I sent mine to Ollies to be blasted, tumbled, have the studs removed and flanges surfaced. As you can see, the manifolds are definitely bright magnesium under the chem film and corrosion.

Next step is these will be plated, flash copper at first and then cadmium with a chromate conversion coating to resemble, if not perfectly match, the finish on the originals. Then the studs get tumbled and black-oxide coated and go back in.

A lot of work but required if you want it to be original appearing.

Also, what junior engineer designed these outer manifold tubes? Unlike the later black Zenith manifolds these are not a straight shot, but curved tubes that have a strange oval port cross section. I wonder what they do on a flow bench? I'll see what I can find out.

[jcge]

John - don't forget that descriptions of surface finishes are for NEWLY PLATED finishes, and not after X years of exposure in an engine bay... (I guess hence your notes about the finish under the bracket....although don't discount the effects of metal to metal contact over time)

Might be worth researching how the finishes change over time due to exposure (not easy as I know you've already encountered the "secrecy" of even the original finishes...)

What about Dow #1 (acid chromate) "golden yellow, often with iridescence"

Have you tried contacting the Porsche museum / factory ?? Surface finish would be specified on all component drawings...

Sorry I can't provide any really useful suggestions..

Regards
John

[jcge]

Originally Posted by john_cramer

what junior engineer designed these outer manifold tubes? Unlike the later black Zenith manifolds these are not a straight shot, but curved tubes that have a strange oval port cross section.

Might just be result of how the patternmaker implemented the transition..."offsetting" a straight length of round tube can deliver a similar result

(leave us poor junior engineers alone !!)

Regards
John

[304065]

Gents, thanks for the input. I'm not picking on Junior Engineers. . . but I do believe that the manifold design was a hurry-up job, given that customers were holing pistons with the Solex carburetors and Porsche was under pressure to get something done, quickly. . .

"Ach, ze Vergaser from ze Lancia ist too narrow fur der zylinders! Call Ing. Strauss, ze new-hire, und tell him zat his vacation is on ze line unless ve have a manifold by halb-nine uhr tomorrow morgen!"

Noah: Magnesium is like butter, you could port it with a chop stick probably. It would be just my luck that the cross sectional area is exactly the same as a circular port and that messing with it would throw the flow off. It's a pretty short run but I have to at least give the factory the benefit of the doubt.

Look at the curves of those runners? See how they were designed with a French Curve? See how the bosses for the studs protrude downward past the flange? Look at the D-shaped holes in the strengthening rib, asymmetrical. Some pattern-maker actually worked pretty hard on this. Now if you compare the later Zeniths, those are basically a straight tube.

[NY65912]

The manifolds are looking good John. How are we going to get that irridesent look?

If I remmember General could not handle the magnesium, so who's gonna plate the manifolds.


Happy Holidays

[304065]

Mike, I am going to have them flash plated copper and then plated cad. The reason GP couldn't do the job is because the acid they use to activate for the cad would eat the magnesium away. With a flash plate of copper in place, the copper is activated and the cad adheres to that. Hexavalent chrome is then used for the iridescent look and away we go, on to the next problem!

Is there a Zum Stammtisch in our future? Does a chicken have lips?

[Hirth547]

Bumping to the top, very interested to learn if you succeeded in plating the manifolds

[304065]

They are still in my closet. I am going to use Henkel chromate on them I think.