De-Chrome with Lye

[bfrd]

I have been struggling with de-chroming some aftermarket wheels from Pegasus. They laughed at bleach and oven cleaner. I went to the auto parts store and bought some CRC brake cleaner. That did make a dent, but still not enough. Then the lye I ordered from Amazon came in. Lye is also known as Caustic Soda. In either case the chemical designation is NaOH - Sodium Hydroxide.

I watched Will Pattinson's video and he showed great results with draino. As he explained this is simply a high concentration of NaOH. I didn't have good results with draino, so I decided to go straight to the source and use NaOH by itself. I think the only thing in Will's video that I didn't agree with is that everyone has success with a single product. I have never had great success with anything. Personally, I have never stripped Tamiya chrome. I have only felt the need to strip Revell, MPC, and AMT chrome so far. Bleach gets most of the job done, but I always had to follow up with oven cleaner. Once that was done I am left to deal with the binding agent. Lye has left nothing behind. I think a more in-depth test with different chrome might be useful.

Just be careful, Sodium Hydroxide is a powerful base and can hurt you if precautions are not taken. Bases are just as dangerous as acids. I actually have a degree in chemistry and worked in a lab so I am familiar with this stuff and am comfortable using it. If you are not comfortable handling a chemical like this DO NOT TRY IT. I know most of us here are adults, but children should not do this without a parent.

Will explained that most modern chrome plating is Aluminum, so why does a base work? Aluminum is an amphoteric metal and will readily react to either an acid or a base. Let's look at the reaction.

aluminum + aqueous sodium hydroxide + water ⟶ sodium aluminate + hydrogen

So what you get is a compound called sodium aluminate and hydrogen. So just to be safe, don't do this around any open flames as hydrogen is very flammable.

Now that we know what will happen, let's make it work. You will want to add the NaOH to the water and not the other way around. I can't give specific amounts because I have no idea of the volume of plastic you need to de-chrome. I used a small glass and filled it with water. Adding lye to water is highly exothermic so the water will get very hot. Be careful that you don't do this in an enclosed room. The heat produced is enough to cause the water to vaporize and you really don't want to breath in that vapor. A cheap paper mask isn't going to protect you.

I would recommend using lower concentrations of NaOH multiple times rather than a single high concentration. I used about a teaspoon of lye in about 500 mL of tap water. I didn't measure so I am estimating the amounts. It may take a little bit of mixing to get all of the NaOH dissolved. The solution will also be a little cloudy at first, this should clear up. Once mixed just drop the parts in the container. You should see a reaction almost immediately. The equation shown above will reach a equilibrium where no additional Al will be converted. Once this is reached extra time really won't help. I left it alone for about 30 minutes and the chrome was close to removed, but not completely.I just dumped the glass into the sink and rinsed everything off and then repeated. Keep in mind that aqueous NaOH is safe to dump in the sink. One additional word of caution, a base will not immediately "hurt" when it gets on your skin. It will burn you if not rinsed off, so be careful. A base will feel slippery (just like soap) so rinse with just water. I would recommend wearing gloves, but be careful that no solution gets trapped inside of the glove and on your hand. After, rinse your hands and forearms well no matter if you used gloves or not.

Let me repeat that NaOH can be very dangerous. Just because I am dumb enough to not be warned off of this doesn't mean that you should. My days of being in the lab have long past and I no longer have the equipment I once had. Please don't try this without being confident you can do it safely.


This is what I used. There are cheaper products, but I chose to get something that was more pure.

[Twokidsnosleep]

I actually have a degree in chemistry and worked in a lab so I am familiar with this stuff and am comfortable using it. If you are not comfortable handling a chemical like this DO NOT TRY IT

^^^^^^This is the most important part of the post
Super strong chemistry going on here, not for the faint of heart, deaf, dumb, blind or especially stupid.
I am surprised you can get it online actually

[barrythornton]

Hardcore. Best known for disposing of bodies, will rot flesh no problem.
But hey, that chrome gotta go ! so whatever works

I am surprised you can get it online actually

get `Caustic Soda` anywhere, used for clearing drains .... dissolves fat and food waste in the pipe.
And if you can hide the crystals in a bait, its good for Rats ..... or bad.

[Twokidsnosleep]

Hardcore. Best known for disposing of bodies, will rot flesh no problem.
But hey, that chrome gotta go ! so whatever works

I am surprised you can get it online actually

get `Caustic Soda` anywhere, used for clearing drains .... dissolves fat and food waste in the pipe.
And if you can hide the crystals in a bait, its good for Rats ..... or bad.

Ya, see what I mean