[dataway]

Anyone know if Evaporust removes zinc plating? I just treated my hood latch an the Evaporust did an absolutely outstanding job on it, but it looks as if it also removed the factory zinc plating.

I was about to buy a repop latch because mine was filthy, rusted in places, zinc worn down. My usual go-to would have been bead blasting but figured I'd never get it all out of the mechanism and it would be grinding forever. So cleaned it with kerosene, then brake cleaner, then gave it the Evaporust treatment ... freaking thing looks like new bare metal now.

The factory cadmium plating on the latch hook was still good, nice and gold ... that's gone now, so wondering if the Evaporust removed all the plating. Looks like it, all the parts are a uniform white/gray metal now.

Anyone ever try re-plating the entire latch since it doesn't come apart?

[Shiny]

Good question. Quick click on their FAQ page suggests it won't dissolve zinc:

"EVAPO-RUST® works through selective chelation. This is a process in which a large synthetic molecule forms a bond with metals and holds them in solution. Most chelating agents bind many different metals. The active ingredient in EVAPO-RUST® bonds to iron exclusively."

and (brass being a copper/zinc alloy):

"Can I clean brass, copper and aluminum with EVAPO-RUST®?
No, it will not clean or damage any of these metals."

But maybe there is a "secondary" effect once the iron goes into solution? Was there noticeable sludge in the container? This might happen if zinc dissolved and "displaced" the iron, causing it to react and precipitate with another ion. They mention the iron is actually held in solution by a different sulfur-bearing chemical than the one that dissolves the rust.

[dataway]

I found less sludge than I expected to find. I've found it to be pretty gentle to most metals other than iron ... as the instructions suggest. Possible it just altered the finish. It definitely removed the chromate conversion on the latch hook zinc plating. It did such a nice job that if it wasn't sealed I would have thought maybe I had put a little muriatic acid in it from one of my other "experiments"

Left an extremely uniform finish on all parts of the latch, almost as if it pulled zinc off and redeposited evenly on the whole thing.

Today I'll pull it out of the bath and rinse it off well and let it dry .... see if any of the previously zinc plated areas shine up like they should. Perhaps find a small area and put a drop of muriatic acid on it and see if it reacts with anything.

Thanks for the input.

[bkmont]

I used Evapo-Rust on an original rusty horn relay. It worked fantastic!. I used a brush to clean all the loose rust, dropped the relay into a mason jar of it and let it sit overnight. Rinsed it with water and dried it out with a heat gun. It cleaned right up and it works.

So I decided to try it out on a froze up Hi Note horn. I filled the horn up with it and let it soak too. After a water rinse and blow dry, Walla! the horn started working.

It's been about a year since I did this. Relay and horn still working.

[Bentwheelbob]

Member Norwood on this board does concours restorations of hood latches. They are completely disassembled, replated with correct finishes and then reassembled. They are works of art. I’m sure you can find his track on here and send him a PM. If not, send me a PM.

[Norwood]

Here are restored pieces

[dataway]

How the heck do you get them apart and back together again being all riveted? Does it use two piece rivets? IE the small side presses into the large side.

I do my own zinc, zinc phosphate, manganese phosphate and zinc di-chromate and was going to disassemble it and give it a shot but I assumed it had unobtainable one piece rivets.

[dataway]

Here are a couple of photos .... you can see it didn't remove the zinc, but did remove the chromate conversion on the zinc.

Seems in good working order, might need the rivet holding the hook to be pressed a bit tighter.

[marxjunk]

i dont know about latches, but it an incredible carb cleaner...i also did some muncie gears...phenomenal product

[Shiny]

Nice!

That stuff is amazing.

Did the part have a colored (ie yellow or iridescent) conversion coating? You think it's gone or just discolored? I don't think those coatings are very thick nor very dense so they might still be there and just changed color.

What's your plan to finish it?

[dataway]

Definitely removed the colored chromate finish on the latch. Not surprising, the chromate finishes do a good job enhancing corrosion resistance but they are pretty delicate chemically. And yes, extremely thin ... in fact not even really a coating, but an alteration of the surface of the zinc plating.

As of yet .... I don't have a plan Since it appears the base zinc plate is good, and the phosphate in other places .... might just buff it up some and oil it down. Anything else would probably require taking it apart, and I'm not sure I'd be able to get it back together in a way that looked original.

I could try dipping it in gold chromate solution and see it it takes on the zinc plated parts. It shouldn't have any effect on the phospated parts I don't think.

[Shiny]

You might have to acid-dip before chromating which could go after a phosphate or similar coating so you are probably right to feel good about it and leave it alone. It looks great as-is to me.

[dataway]

I was just thinking the same thing. At the very least I'd have to pickle it in a mild acid solution since chromate only takes well to fresh zinc.

The only places that were rusty were a portion of the large side of the rivets and the bracket where the pull rod attaches was pretty bad .... not sure why just that bracket, may have to mask it off and paint the bracket and leave the rest be.

[north]

Any strong acid will quickly attack the zinc coating, if the exposure is very brief the zinc coating will remain effective but will blacken from the reaction with the acid, longer immersion in acid will dissolve the zinc completely. As mentioned the gold-yellow-green type shiny color seen on zinc coatings is a chromate conversion. It's not really a coating, it creates an artificial passivization for the zinc to prevent oxidation before the natural zinc passivization occurs over time. This chromate (hexavalent chromium) process is considered temporary and was to prevent white oxidation if the zinc coated pieces get wet in the first 48 hours after zinc coating is done.

Even today but especially back then it was done with an indifferent idea about quality so every piece has a different color and/or depth to the chromating. This is because zinc plating residue would quickly contaminate the dipping tank and rather than keep it purified it was standard practice to just keep adding more chrome bags to the tank to "compensate" for the impurities. Also if parts went in too hot it breaks down the chrome 6 (hexavalent) into chrome 3 (trivalent) which looks more orangish and is of no use for passivization purposes.

Not that any of us will ever touch enough of this stuff to be an issue but chrome 6 is a well known carcinogen through ingestion and skin absorption..

[Joe's Garage]

Originally Posted by Shiny

You might have to acid-dip before chromating which could go after a phosphate or similar coating so you are probably right to feel good about it and leave it alone. It looks great as-is to me.

That latch looks better than 99% of the latches on restored musclecars out there.

And the other 1% have visited Norwood's garage.......

[Gator67]

I use Evaporust a lot. In fact I keep a small container of it on my workbench and throw rusty things in it from time to time. After a while the solution got real dirty, and I noticed that it would not only still remove the rust, but if I left the item in the solution long enough, it would result in a darkened appearance, just like black oxide. Looks just like quality plating and doesn’t scratch off.

[dataway]

North .... I have about a two pound bottle of hexavalent chromium dioxide (powder) in my shop. I guess it's no longer used in the states but there are still some European manufacturers that use it .... it's described as "Environmentally Persistent" sounds like a scary euphemism for something

I read there is lots of research these days into coming up with a Trivalent conversion that is more effective because it far more friendly to the environment and people.

I guess I'll drop this latch in some oil and let it sit for a few days and call it done.

Appreciate the information folks.