Electrochemical cleaning of stainless steel welds

[BillyBud]

Not sure where a post like this belongs, so this is just a best guess for passing along some knowledge.

I bought a stainless-steel header for a Bugeye restoration project I am working on. The welds were unfortunately all tinged yellow from the heat generated when they were welded. I researched several methods of cleaning this off and arrived at a process which works quite well, and does not harm the rust resistance properties of SS like some other abrasive or chemical cleaning methods.

Using a 6V 6amp battery charger I attached the positive side to the work piece. I bought a stainless fender washer and made a crude “mop” using some cotton string, then attached that to the negative electrode. I dipped the mop in some dilute phosphoric acid (rust converter) and then touched the mop to the welded discolored area. After a few seconds the yellow discolor dissipated and I wiped it away with a paper towel. I finished with wiping the area down with a baking soda solution to neutralize any remaining acid.

I’m sure the header will discolor from heat over time, but at least it will start out all shiny and pretty! Here's before and after shots of one weld.

 

[JPSmit]

great idea! please keep us posted as to long term effects.

 

[Bayless]

Wow, nice.

 

[Popeye]

That is really cool! Thank you for sharing.

Out of curiosity, had you tried Bar Keeper's Friend (Oxalic acid)? I was planning on using it on a project at work, but we decided the welds were inconspicuous enough that they did not need cleaning. (I will remember your method next time around.)

 

[BillyBud]

That is really cool! Thank you for sharing.

Out of curiosity, had you tried Bar Keeper's Friend (Oxalic acid)? I was planning on using it on a project at work, but we decided the welds were inconspicuous enough that they did not need cleaning. (I will remember your method next time around.)

No I have not tried that. BKF does contain an abrasive which I was trying to avoid. What I did was research "removing welding discoloration from stainless steel" and found there are numerous commercial companies that make machines and processes to do this. Lots on YouTube too. It took a fair amount of reading but I finally found all the clues needed to crudely duplicate their processes. This is what sold me, on the cougartron.com website, since this method doesn't harm the steels anti corrosion properties:

The electrochemical method is extremely effective in these cases since it successfully removes oxides from the surface and restores the anti-corrosive passive layer. Brushing and grinding can also remove discoloration but it is impossible to guarantee that proper (re)passivation will occur.

BTW, phosphoric acid alone does not remove the weld coloration by itself, it only works when the electric method I described is used. I know this because I tried it.

 

[BillyBud]

Here's the finished product, which I am quite pleased with. I didn't get every little bit, so I may have to retouch. Unfortunately it turns out the springs are NOT stainless! Maybe have to replace them or treat so they don't rust.

 

[BillyBud]

And this is the "before" photo, what I got from Moss looked like this when I got it.

 

[JPSmit]

so much better!