Evapo-Rust

A Cautionary Tale

People,

This is a great product out on the market that I'm sure a lot of wrenchers from this forum have used. It's a chelating agent, which means it bonds to iron ions, basically dissolving away rust. As I'm sure is common knowledge it works very well and leaves a clean surface.

There is, however, a catch. It will dissolve other oxides. I actually called the company that makes Evapo-Rust, Harris International Labs, to make sure that it would not harm the finish on my carburetor parts. They told me that "since it doesn't have any degreasers or anything like that, it won't remove any paints or finishes or anything except iron rust." I specifically asked about oxide finishes, such as anodizing and zinc/chrome type finishes. Someone may correct me here, but I'm pretty sure that the carb parts on the HSC33s are zinc finished, and in some cases have a yellow chromate hard coating applied. This is pretty standard for carbs I guess (any time they look yellow, my reading indicates that it's zinc with yellow chromate over top).

Well, sadly, Evapo-Rust WILL remove yellow chromate (an oxide, ZnCrO4), and it will remove zinc coatings/platings, presumably for the same reason. My yellow carb parts are no longer yellow. I obviously can't say for absolute certain that all the galvanizing is gone from the other parts, but it appears that way. I stopped using it on any yellow parts after that, and I've clear-coated anything steel that I used the Evapo-Rust on. For what it's worth, after I used the Evapo-Rust on some presumed galvanized nuts and bolts from the bike a couple of years ago, they all have pretty bad surface rust on them now. This didn't happen until I used the Evapo-Rust.

So, the moral: if you use this stuff, I would suggest not using it on anything that has an oxide coating you want to preserve. Or if you do, clear-coat or switch to stainless. I wouldn't write so much about this except that the customer service department at Evapo-Rust clearly should be a little more cautious with their descriptions of the "safe on everything" nature of the product.



Sean

 

Good to know. Thanks for the heads up.

 

That is quite surprising. I had no idea. Thanks for sharing. My experience with Evapo-rust is with parts that I have prepped for replating or paint. I never considered that it would not be suitable for normal cleanup.