Cleaning Oxidation from Steel
 

When I have a new idea to share I'm always a little concerned that everybody already knows about it. But I found something really quick and effective for removing the green/tan/yellow oxidation from steel and brass. I'm not sure it's actually oxidation, but you know what I'm talking about. Don't use this on chrome or other plating. It will cause the plating to blister and peel.

How to accomplish this in under three minutes:

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Muriatic acid (for cleaning swimming pools) is hydrochloric acid, probably 10% to 15%. It can seriously blind you or burn you if you can't get it rinsed off quickly. Yes, I use gloves and goggles to handle the big bottle, then latex or vinyl gloves with eye protection for the small work.

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It's easiest to do on removable parts.. Brush on the full-strength acid and rinse it thoroughly with water. If the crud is particularly thick, you may have to spend one or two minutes brushing the acid, but usually you can rinse right away. Then dry and polish.

You can clean parts while they're still in place if you can block out the area adequately with absorbent rags. Here I use water in a spray bottle for rinsing.

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If you want to try this technique you should know ahead of time exactly where and how you're going to rinse your eyes just in case your PPE (personal protective equipment) fails.

- Winky

Muriatic acid is usually around 31% concentration, a saturated solution of HCl in water.

That yellow powdery stuff is oxidized cadmium, as cadmium plating was once very common before the toxicity of cadmium was appreciated. The leftover acid solution from your cleaning process will be loaded with cadmium, and shouldn't be disposed of down the drain.

Thanks. I guess I'll stop licking my chassis. Actually I will call our local hazardous waste people about this issue. They'll probably say, "Huh?" But they should know how to appropriately refer the question.

Another caveat with the HCl--use in a well-ventilated space and don't mix with other chemicals. Toxic fumes may result.

Actually the muriatic acid sold today is usually the "safer" product as shown above. As far as I can tell, "safer" means a concentration of less than 25%.

I know this is unnecessary (perhaps ridiculous), but I hate leaving loose ends.
To put the potential risks of handling cadmium in perspective, here is some information that is totally uninteresting, but pertinent.

Despite its toxicity, cadmium is still widely used in metal plating and several other industries, and workers' health and industrial waste are concerns.

In workplaces where there is risk of chronic cadmium exposure, typically for five or more hours daily, the cadmium level in the air is monitored and safe levels are established.

The greatest health concern is inhalation of particulates containing cadmium and cadmium compounds. Other routes of exposure are of lesser concern, although ingestion of 30 grams of cadmium (all at once) will likely kill you.

The corrosion of cadmium in the air yields cadmium oxide and, because of air pollutants, some cadmium sulfate. If you drop a corroded screw in hydrochloric acid you can see tiny bubbles and get the rotten-egg smell. The bubbles are hydrogen and hydrogen sulfide.

My opinion is that if you are concerned with handling cadmium corrosion products for health reasons, then mechanical removal is riskier because it is likely to produce airborne particles. Chemical removal would be safer. And if you feel that disposal of the chemical waste is an environmental concern, then you need to be equally concerned with disposal any solid waste from mechanical remove of cadmium corrosion products.

For purposes of accuracy and credibility, none of this information came from Wikipedia.

A few times over the years I used muriatic acid to free rusted wheel bearings. Nasty stuff though.

I use it all the time with great success but you have to know what you are doing with it. Fabulous on aluminum too but will kill zinc and chrome.

I remove rust a lot of the times through the electrolysis rust removal method. I have had great luck with it. I restored a lot of old woodworking tools to fix cabinets and such. Its the least damaging way I have found. It doesn't remove any metal , it just causes the oxidation to release. If I have something with bolts rusted it will cause them to break free. But don't use it on chrome as it will cause it to loosen and come off.

On aluminum I use oven cleaner. I check it every few minutes with a fine steel wool piece to see if the tarnish is off. After it is easily removed with the steel wool I wash it off and go all over the aluminum with scotchbrite. I then polish it with a product called siver wadding compound. Its a silver cleaner in walmart. I have gotten almost a mirror like finish on aluminum doing this.

There's "Naval Jelly" but don't use it on your naval... For removing rust. Think it's the same as muriatic acid.

Naval Jelly is phosphoric acid mixed with a thickener. Much milder than muriatic.

I use Naval Jelly all the time for cleaning metal parts like that shown in the first post. You need to let is sit on for 5-10 minutes though.

- Geoff

For heavily rusted small parts, such as nuts and bolts, I sometimes immerse them in Naval Jelly overnight, then easily remove the black accretion with fine steel wool to leave a clean metal surface. On chassis rust spots, however, it leaves an area that appears different from the surrounding metal which I can never get to match.

I don't know what the stuff is, but you can most likely use the etching solution used for auto painting. After getting the paint off, you wash the body part with this watered down etching solution before priming. But then you better coat it with something...... Get it at auto paint supply, I use to have some, but not currently or I would just write in what its active ingredients are..... It gets ALL of the oxidation off....

I've had excellent luck using a wire wheel to remove oxidation and polish metal.

The auto painting solution is likely "Metal Prep", which coats the surface with phosphate crystals. This increases adhesion between metal and paint.

If you use muriatic acid, it's a good idea to neutralize the residual chemicals after rinsing with a caustic solution, such as oven cleaner or soap.