Electrolytic Mill Scale Removal

[rwm]

Does any on know (has anyone tried) to use an electrolytic de-rusting bath to remove mill scale on hot rolled steel? I know it does a great job with rust and paint. I have never tried it to remove mill scale. I don't want to waste the time to set it up if it will be ineffective.

 

[tweinke]

I have removed mill scale with vinegar and it worked pretty good. Soaked it overnight and gave it a good scrubbing with a wire brush a couple of times during the soak.

 

[MrWhoopee]

Vinegar here too. Surprised me how well it worked.

 

[93xs2003]

Try citric acid. I prefer citric over vinegar.
I find it works faster, and doesn't smell as much.

You can order food grade citric acid as a powder online or possibly find in grocery store or pharmacy. I ordered "Milliard Citric Acid 100% Pure Food Grade" from Amazon.

 

[Alcap]

Do you need to do any type of neutralizing after any of these cleaning ?

 

[SLK001]

Do you need to do any type of neutralizing after any of these cleaning ?

The light acids, like vinegar and citric acid, only require a rinse with water. Stronger acids, like HCl, should be placed in a bath of baking soda (NaHCO3) for a couple of minutes, then rinsed with water. The freshly exposed steel with have a tendency to flash rust, so if this is a problem for you, coat the new surface with a light oil.

 

[GeneT45]

Try citric acid. I prefer citric over vinegar.
I find it works faster, and doesn't smell as much.

You can order food grade citric acid as a powder online or possibly find in grocery store or pharmacy. I ordered "Milliard Citric Acid 100% Pure Food Grade" from Amazon.

I'll have to try this. I had pretty lackluster results with vinegar (though I see stronger 'cleaning vinegar' now...

Citric Acid is sold at WalMart in the canning section - I use it as the acid for an acid/baking soda rocket my granddaughter enjoys.

GsT

 

[jbaccell]

Try citric acid. I prefer citric over vinegar.
I find it works faster, and doesn't smell as much.

You can order food grade citric acid as a powder online or possibly find in grocery store or pharmacy. I ordered "Milliard Citric Acid 100% Pure Food Grade" from Amazon.

How much citric acid to say a gallon of water? I'd like to try it for removing rust as well.

Thank you,

Joe

 

[93xs2003]

I don't really have a recipe.

Start with maybe 1/4 to 1/2 cup of citric acid to one gallon of hot tap water. If you aren't seeing mild activity (slow bubbling, yellowing then darkening of water) in 10 min, add another 1/4 cup.
(I have a short length of 4" pvc capped and turned up on end. I balance it in an old truck disc brake. Depending on metal load, maybe a gallon will fit. If I was cleaning hrs today, I'd probably start with "two scoops." guessing that is about 1/4cup. It's cold here, so I'd place the whole stack in a bin as a spill basin and do this indoors.)

In hot weather and relatively smooth and clean structural tube, you might be done in a few hrs. In cold weather or crusty and pitted hot rolled you might be at it overnight or for days. Wipe down with scotchbrite or wire brush periodically to gauge progress. I expect scrubbing/scratching helps undermine the oxide.

 

[93xs2003]

I just rinse with water, then dry immediately.