sodium bisulfate scale removal

[NickWheeler]

I'm hoping some of you guys that use this can tell me about it.

I've been looking into sodium bisulfate for removing forge scale off of my blades prior to grinding.

I like Vinegar because it's cheap, easy, and if I spill some in my protein drink I won't have to induce vomitting (well, the taste may cause me to want to, but I won't have to)......

But I've heard blacksmiths talk about using NaHSO4 and just recently saw Kevin mention using it in his shop.

So it's available for lowering the Ph level in your pool....

But then what? What are your methods for actual use?

I read the MSDS on it and says to keep it away from heat, so I'm assuming I better not warm it up prior to use

How long does a blade have to soak in it? (I know there are variables like how badly your work is scaled, but I'm looking for an average).

Thanks for any help

 

[Phil Dwyer]

Hey Nick,

Not a direct answer, but some info anyway:

Sodium bisulfate is a common compound used to make pickling solutions for jewelry making. A common band name is Sparex. A mixture of 1 to 4 (sb to water) is typical. We always heated our pickle, either in a pyrex dish on a hot plate or in a crock pot (both on low, non-boiling settings). This removes oxides (scale) and fluxes pretty well. Although we never put iron in our pickle, it should work fine for it. The reason we didn't, is that we didn't want it "contaminated" for our precious metals, which would get copper plated if iron was introduced.

I'm using vinegar for my steel right now, but it does take a while (overnight). I've tried a muriatic acid substitute too. It work well, but was pretty aggressive, even in just a few hours. I too will be trying sodium bi-sulfate, probably in a big crock pot on low. Let us know how your trials go.

Thanks, Phil

 

[NickWheeler]

Thanks Phil!

I got quite a few jewelry applications with a few various Google searches.

Pickling was indeed the word used most frequently. I've researched "pickling steel" before, and it usually refers to sulfuric and hydrochloric acids. Neither of which I'm very keen on having in the shop.

I'll locate a local pool/hot tub supply outfit and then give this stuff a try.

Thanks

 

[fitzo]

Nick, sodium bisulfate can be considered the "half-acid" form of sulfuric acid, partially neutralized so it isn't as potent and can be kept as a solid. (Think toilet bowl cleaner, Sani-Flush.) It's still considerably more acidic than vinegar, so I would expect your scale-removal times to be reduced significantly. Heating the solid is not recommended, but you should be able to heat the solution moderately without concern. Be wary of any hazy fumes...they may well be sulfuric acid.

 

[Bruce Bump]

Has anybody tried sandblasting the scale off? I always wanted to try that.

 

[sunshadow]

Has anybody tried sandblasting the scale off? I always wanted to try that.

if you use an aggressive enough sand to take the scale you erode the metal (which is softer than scale) I have been using sodium bisulfate for scale removal and discovery etch for damascus since Kevin mentioned it at Ashokan, make sure that your ventilation is good and that you neutralize in sodium bicarb solution so that any pits or cold shuts don't leach rust later. The sodium bisulfate works well. For jewelry I use the Rio Pickle brand, for knives I just use "PHDown" brand from the hot tub supply store. Don't use Sparex, it's got oily brown crap in it. I talked to another jeweler who was familiar with where the stuff comes from, he said sodium bisulfate is an industrial waste product, (kind of like food grade gelatin most of which has come from Eastman Kodak the world's largest manufacturer of gelatin. The stuff we eat is gelatin that isn't pure enough for film. It has to be pure to parts per billion standards for film, only parts per million for food) anyway the process that sparex comes from is kind of messy as far as what it leaves behind.

-Page

 

[burke531]

Has anybody tried sandblasting the scale off? I always wanted to try that.

Bruce, I have a blast cabinet with galss beads in it that I sometimes use. I works OK but is slower than a snagging wheel on a seven inch grinder.

 

[NickWheeler]

Thank guys!

Fitz, I was hoping you'd chime in, but didn't want to call you out specifically. Thanks my friend

 

[Stacy E. Apelt - Bladesmith]

Sodium Bisulfate is used as a jewelers pickle for precious metals. It will remove oxides, scale, and fluxes. Be aware that it will also dissolve steel and iron if left too long or too concentrated. The way we remove a broken drill bit or tap from gold is to leave it in the pickle pot for a day or two - no more tap. As with all acids, use safe chemical practices, and have a plenty of the anti-agent handy ( in this case water and Sodium Bicarbonate).
I mix my acid from 7:1 to 10:1 (H2O:SB) for gold and silver.
Stacy

 

[sculver]

Has anybody tried sandblasting the scale off? I always wanted to try that.

Bruce,

I've blasted scale off using aluminum oxide abrasive at about 60 PSI. I thought that it worked pretty well.

 

[Kevin R. Cashen]

I started using it because vinegar was too weak to get things done like I wanted, muriatic fumes way too much and I don't like soaking my steel in hydrogen based acids, so I was using sulfuric acid for a while but didn't like the nasty stuff sitting around, so I gave the bisulfate a try for an effective yet tamer solution. I never did the blasting thing becasue I have a cabinet that I don't want to refill anytime soon and while doing my fine work I like to know I am using the silica bead media of a uniform grit, not the media mixed with assorted chunks of iron oxide and black glassy flux.

 

[Tai Goo]

I just rub it with a stone.

It might take 5-10 minutes of “manual labor”.

Oh my gosh!… did I just say manual labor?…

It’s that easy!

 

[Plain ol Bill]

Nick as you know I use my blast cabinet to remove scale and love it. I tried vinegar and such but just don't have enough patience for it. Blasting with garnet or silicon oxide will rip that crap right off.

 

[NickWheeler]

Hey Tai- You can go to work with me and swing a 12 pound spike hammer for a 12 hour day... driving RR spikes into hardwood ties and we can talk about whether or not I am willing to do manual labor.

Or maybe packing 100 pound bags of coal across a roof all day and then evenly distributing them inside of a 20' tall, 10' diam tank with only a tiny man-hole on top for entry/exit.

Or maybe.... Well, you get the idea.

 

[Dan Seaver]

I just rub it with a stone.

Have you tried using a sen/draw knife for scale removal yet? Its the best method I've used so far. :thumbup:

 

[Tai Goo]

Dan, No.

I always figured the scale would dull the draw knife. It must get underneath it and pop it off. I'll try it.

 

[nthe10ring]

The sen sounds like a good idea, what approximate angle do you have on the edge.

Jerry Fisher

 

[Dan Seaver]

Make sure you wear goggles Tai. I made the mistake of thinking that since its a hand tool removing scale would be no big deal... wrong. It sends scale flying when you do it... in your eyes if your as stupid as me!

Jerry I have the edge convexed on one side and flat on the other, the steel is about 1/16 at the edge before its convexed. Not sure if that helps you at all. This is just my first sen, I'm going to make many more to find what works best for me. :thumbup:

 

[Tai Goo]

O.K. Dan thanks. I hate getting scale in my eyes.

I usually use the sen type scrapers pushing away from me rather than drawing towards me anyway though.

 

[Guy Thomas]

A sen for scale removal, what an intriguing idea! I'm definitely going to have to make one of those soon, though I seldom begin working on a knife immediately after forging so an overnight vinegar soak is usually no big deal.