Friday, April 3, 2015

Putting Rust to Bed

& is used with permission.
Three weeks ago, I talked about rust prevention. Today I'm going to do a follow-up and talk about ways to remove rust from objects.

An Abrasive Tool and Lots of Effort
This is the default method for removing rust. As you expect, it requires a significant investment of time and energy to remove the rust, and there's always the risk of using too abrasive a tool, or too much elbow grease, and damaging the surface of whatever you're trying to fix.

Fortunately for people without a lot of time (or who are lazy), there are other ways to remove rust. These are just two examples, and I bought both of them at my local auto parts store.

Rust Dissolvers
There are actually two forms of dissolvers:
  • Chelators chemically bond with the rusting agent. Usually in jelly form (the most popular is called Naval Jelly), these solutions can be easily washed or wiped away, carrying the rust with it. 
  • Acids (typically mild phosphoric acid) eat the weaker rust down to the stronger steel. However, this will also remove any paint or bluing on the metal.

The brand that I bought, Loctite Naval Jelly, seems to be a combination of the two, as it is both a jelly that needs to be wiped away and a phosphoric acid that attacks the rust.

I bought this at my local auto store for around $7 + tax for an 8 oz. jar; Amazon costs half that but also charges shipping, so it comes out to roughly the same.

The good news is that it goes on easily, works quickly (within 5-10 minutes), and comes off just as easily. The bad news is that it leaves treated metals looking a bit scorched -- which I guess they were, as this is essentially chemically burning the rust away. Fortunately, a lot of this scorching can be removed with some light scrubbing and a lubricant like CLP or WD-40. And you will want to use those; Naval Jelly does not protect metals from subsequent rusting, so if you return your tools to where they rusted the first time, they'll rust again without protection. Again, see my previous article on rust prevention.

Rust Neutralizers
Here is where things get interesting:  did you know there's a good kind of rust?

Bad rust -- aka orange rust, aka what everyone thinks of when they think of rust -- is Fe2O3. It's also chemically unstable and aggressive, as you can see by the way rust spreads across metal and eats it.

But the good kind of rust -- Fe3O4, aka black rust -- is far more stable. It doesn't eat anything; it just forms a layer across metals. This means it's perfect for protecting steel and iron tools from further rusting. In fact, it's so perfect that "black oxide" is a common tool coating.
It also happens you can buy a chemical that converts orange rust to black rust. The kind that I bought, Loctite Extend, goes on like a thin paint and then dries (after a few coats and 24 hours of curing) into a black layer that looks and feels like latex paint. This layer can then be painted over, if desired.

The main drawback to this product is that instructions say it needs to be shaken before use, which produces bubbles, and bubbles in your coating result in circles and pits in the black oxide layer. I also found it very difficult to get an even coating when applying it, giving the finished product an appearance of being amateurishly painted (which I suppose it was).

I bought this at my local auto store for around $10 + tax for an 8 oz. jar; Amazon again costs half that but, again, gets you with shipping charges.

Here are some before and after shots to demonstrate how these two rust solutions work.

 This is before treatment. The top tool bit is used both as a control, and to demonstrate the natural color of the metal.  The middle tool will receive Rust Dissolver, and the bottom Rust Neutralizer.

As you can see, the half of the middle tool treated with Rust Dissolver is indeed darker (the aforementioned "scorched look") but is recognizably rust-free.  The bottom tool has been treated with Rust Neutralizer and has a light black oxide coating. If applied carefully, fine marks and etched writing will not be obscured, but a light touch is required for this.

I like both of the these products; they're priced well, do a fine job, and I still  have lots left over. The only real question is "Which one do I use?"

If you want your iron or steel tool to look nice, use the Rust Dissolver and then polish away the scorching. It ought to look mostly new after a few minutes' work.

However, if you plan to keep your tools in a harsh environment, or simply want to "fix it and forget it," use the Rust Neutralizer to protect your tools. So long as the coating isn't broken, your treated tool is protected.

No comments:

Post a Comment

The Fine Print

This work is licensed under a Creative Commons Attribution- Noncommercial- No Derivative Works 3.0 License.

Creative Commons License

Erin Palette is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to