I finally got around to doing this so here are some pictures.

Much of the stock I use is .25 thick hot rolled plate and strap cut from sheets 5 X 10 feet. It is very smooth with mill scale extremely resistant to removal. I have twisted pieces of this red hot and had it not take rust outdoors for over a year. I have also hammered it thin while red hot still retaining this scale which challenges wire wheels and sanding disks. Dipping it in water red hot won’t even phase it most times.

So this being the toughest scale I have to remove, for this experiment it’s mostly what I used. I haven’t had very much trouble with mechanical scale removal after forging bar stock but the hot rolled plate I’m able to obtain can turn a newer flap disk into a smooth buffing wheel in no time

I threw some parts in a bucket and filled it with plain white vinegar just to the tops of the parts for this experiment. You can see on one part where the scale came off half way up. Patches of scale were left on top of some the pieces where the scale escaped the vinegar.

The finish came out very flat grey beautifully clean texture hiding dull. I wire wheeled some of the ends of some pieces and the finish shined like jewelry and brought out texture. You can see where the scale which escaped the vinegar resisted removal from the wire wheel on the flat piece.

The parts were cleaned up with a plastic scrub brush in a bucket of warm water with a drop of dish detergent.

Since the scale from the stock yard always gives me more trouble than that which is produced from my forging, I plan on setting up to do this to some of my stock as a pre-treatment. A long piece of PVC capped both ends slit in half would be good for soaking a bar. Spears.

Well known to blacksmiths. Note that pre-treating bars may run into difficulty where they have been spattered with oil or grease; however after the piece has been through the forge that should not be a problem...

Neutralize the vinegar with baking soda and lots of water when you finish the soak.

Neutralize the vinegar with baking soda and lots of water when you finish the soak.

Dish soap seems to be adequate with lots of water for neutralizing vinegar, and it is a lot easier to work with than the baking soda. For more potent etches than 5% acetic acid (vinegar), yes, use baking soda first.

Phil

Curious how long does the soak need to be on average and does the vinegar lose strength afterwards or can it be reused ?

I usually soak for a couple of days with a couple of wire brushings and turning along the way. Some pieces need another day or so. The vinegar will weaken but usually you can do several batches (a half dozen or more) before it gets so slow as to need to be replaced. I like to use household ammonia to clean and neutralize after soaking... just a cup or so in a bucket of water.

Thanks Bigfoot

Great questions and information. Thanks guys. Spears

I use the vinegar till it stops working in a day or two.

Phil

Do not leave longer than 1-2 days max. I have a small 40 lb vulcan anvil that was given to me by a friend. It was in pristine condition except for a light layer of rust all over it, he thought it would be easy to remove the rust by dropping in vinegar overnight.... when he remembered to get it out more than a week later it was ruined. The nice smooth casting was BADLY pitted and all the slag eaten out of the wrought top plate. I keep it because the construction is easy to see and it is interesting.
smith

Do not leave longer than 1-2 days max. I have a small 40 lb vulcan anvil that was given to me by a friend. It was in pristine condition except for a light layer of rust all over it, he thought it would be easy to remove the rust by dropping in vinegar overnight.... when he remembered to get it out more than a week later it was ruined. The nice smooth casting was BADLY pitted and all the slag eaten out of the wrought top plate. I keep it because the construction is easy to see and it is interesting.
smith

I guess that answers the question for those folks looking to give their projects that weathered aged pitted look. Very good to know. Thanks.

It does not pit "good metal" in my experience but it will eat out bad metal with inclusions and imperfections. (Vulcan's are known to be lower in the quality scale than most anvils) I often leave pieces forged from new mild steel in from one weekend to the next with no problems.

It does not pit "good metal" in my experience but it will eat out bad metal with inclusions and imperfections. (Vulcan's are known to be lower in the quality scale than most anvils) I often leave pieces forged from new mild steel in from one weekend to the next with no problems.

That's good for relieving my stress; knowing I can be procrastinating and forgetful with my pickeling and my work won' t be going to hell in a hand basket. Or should I say "soak container".

The anvil was cast body with a wrought top plate on the working surface all the way to wrap around the tip of the horn. Steel forgings should be ok for longer as Thomas said.

I had an old adze I left in almost a month and when it came out it clearly showed that it had been made from wrought iron with a very thin plate of high carbon steel pad welded to it to make the cutting edge. I ended up lending it to a local MatSci Prof to show his classes how it used to be done! The weld line did preferentially etch though.

I like to see processes like these that are usually hidden that show how it was made or what from.

I knew that they used to be made that way but what surprised me was how thin the Hivh C layer was, less than 1/8"! And this was a factory forged adze not a frontier special

I knew that they used to be made that way but what surprised me was how thin the Hivh C layer was, less than 1/8"! And this was a factory forged adze not a frontier special

I expect it was thicker when welded and ground to that during manufacture. Modern industry does a lot of grinding because it is a quicker way to get good tolerances, I am sure it has been done this way for a very long time.

Phil

You could also use citric acid. It gives better results and is alot faster.
When your smithing is done leave it overnight in a bucket with water and citric acid.
The next day brush it up under flowing water and you have it nice and clean without any damages on the steel.

Greetings from Germany,
Sven