Topic: Reverse plating to remove rust

I feel that I am in over my head posting here so please be kind  if possible.  Of late I have been restoring small engines and was glad to find this forum.   If you don't want to go into this maybe you can point me in the right direction so I can figure it for myself.

There are how-to's all over the net talking about the process using sodium carbonate (washing soda) at 1 Tbs per gallon of distilled water and a battery charger.

I have built a 1 gallon test tank and it worked using water filtered with an instapure filter on the tap.  I doubt it its effectiveness because topping off the tank mid cycle will cause a new layer of brown foam to form on top.

Next I want to build a larger setup and would like to use water right from the tap (no hitting the cheap hobbist).   

(1) I am wondering if I can just run the tank with some scrap at first and attract the unwanted minerals to the anode then save the clear water and clean the tank.

(2) Or would it work to use sodium tetraborate (borax) to bind up the minerals.  It is used in laundry machines for that reason.  I seen where one person was using it in place of washing soda.

(3) I have a background in micro controllers and was wondering if a pulsed DC at a higher voltage would speed up the process without too much heating or hydrogen embrittlement.  

Thanks In Advance

Last edited by 3v0 (01/09/2014 - 06:10 PM)


Re: Reverse plating to remove rust

Update:In case anyone else gets here with the same problem I will document what I am trying.   I am blogging about it at http://zombieengines.blogspot.com/2014/ … lysis.html


Last edited by 3v0 (01/10/2014 - 03:17 PM)


Re: Reverse plating to remove rust

Hi i am new here.I don't have any knowledge about that.Sorry.

Y Strainer

Ray Kremer

Re: Reverse plating to remove rust


Okay, this is basically like a rough and tumble elctroplating operation, except that instead of encouraging metals dissolved in the bath to deposit on the part as zero valence metal, you are encouraging the rust to cast away its oxygen and convert back to zero valence metal. That's the chemistry in a nutshell.

The anode here acts to balance the reaction. The DC power source is sending electrons to the part (the cathode) so it must take electrons from the anode. This generally means the anode is going to dissolve by converting its metal to metal ions. You're not going to "attract the unwanted minerals to the anode". If anything you could use some clean scrap as the cathode to plate the dissolved metal onto it, at least in theory. Depending on the bath conditions and metals involved the current may go more towards producing hydrogen and oxygen gas (electrolysis of water). Using complexing agents or chelating agents to bind up the dissolved metals is fine too.

Tap water should be fine. Water purity isn't much of an issue here since you need to have stuff dissolved in the water just to let the current flow.

I'm not sure what if any difference pulsed DC will make. Certainly for industrial electroplating and electropolishing, very fine and specific current control is used to maintain good results. For a rough and tumble rig like this, you may not notice much of a difference.


Re: Reverse plating to remove rust

Here are my thoughts on the questions you listed:

1) No, you can't strip some scrap, attract the unwanteded minerals to the anode, and keep the "clean" water. It just doesn't work this way.  As Ray said, you need to have some minerals in the water to conduct electricity.

2) Borax is not nearly as good as carbonates to soften hard water and increase alkalinity. In your case, hard water shouldn't be a huge issue. I wouldn't worry about minerals in the water. I'd stick with the washing soda as my source of alkalinity.

3) A pulsed DC supply might be beneficial, but I'm not sure the effort of making a system is worth the outcome. You would be better off agitating your solution with either a pump or low-pressure air.  You might also see better results if you put a bit of (low-foaming) surfactant, like the kind they use in automatic dishwashers.

-Dustin Gebhardt, CEF

Advanced Manufacturing/Finishing Engineer


Sanford, NC