Restoration Tip: Electrolysis Derusting

[Steve Rooke]

One thing that concerns me about using a derusting tank is Hydrogen embrittlement. I do not understand it, but after doing some reading on the web I would he hesitant in using it on critical parts such as wheels or a chassis. Apparently it is a major concern in the electoplating industry. Anyone the wiser?

That said, I have no problem using it on panels or minor parts. Its the cleanest way I know of stripping paint. if I only could build a bigger enough tank to fit my cab into.

Steve

[sth65pac]

Originally Posted by Steve Rooke

One thing that concerns me about using a derusting tank is Hydrogen embrittlement. I do not understand it, but after doing some reading on the web I would he hesitant in using it on critical parts such as wheels or a chassis. Apparently it is a major concern in the electoplating industry. Anyone the wiser?

That said, I have no problem using it on panels or minor parts. Its the cleanest way I know of stripping paint. if I only could build a bigger enough tank to fit my cab into.

Steve

Steve,

Whoo............... A high tech thing for Ye Maple Leaf Up!

I think that this problem (only) relates to alloys and not to regular iron/steel. Hydrogen Embrittlement occurs when stripping paint from an alloy, using some chemical strippers which are methylene chloride based (chemical paint stripper). NOTE: The alloys can include high strength steel but these would be rare in 1942, and would be like the special cross member in my Ford Capri convertible.

If embrittlement occurs, then the alloy piece in question can lose it's physical strength, and cause a catastrophic failure. Most chemical strippers have this compound in them. It affects predominantly aluminium and magnesium alloys.

It is critical in stripping alloy aircraft parts that the correct stripper is used. It was a very expensive lesson for my previous employer to learn that they had made a few million in parts worthless by stripping with a no frills stripper instead of media blasting them!!!

The damage by chemical stripping: It is sub-atomic and the parts look normal, but their strength is about ten-fold less!

As every alloy is made differently, I am personally wary of chemical stripping and my best solution to this issue is use plastic media blasting. Some blasting can be detrimental too as it can 'case harden' metals and intoduce micro-pitting which will lead to cracks and corrosion. (my personal dislike of sandblasting relates to this)

Some of you have heard of 'pickling' (in alloys) then Hydrogen Embrittlement with chemical stripper is the reverse!

It is a large subject but hopefully this will enlighten readers a bit more... It appears that the person on the WWW whom you have taken your data from does not understand what happens either.. unless a wheel contained alloy, it is impossible that it would be affected by hydrogen embrittlement. As for other parts ie Chassis and the like, they would primarily relate to alloys, not steel....lest of all your good old iron CMP chassis.

Ian

[Ralph Volkert]

There is a lot of info in this thread some good some ... not so

I used to work at a chemical plant specialising in Iron salts and worked with the chemists in the lab closely. I also worked for dept of Metallurgy at Queens University and got to pick their brains to for conservation projects!
(I also got access to the art conservation books at their Library)

Here is a link to a very good article outlining the proceedure and science of electrolysys. (http://myweb.tiscali.co.uk/andyspatch/rust.htm#achieved) The author has most of it right.

Notes!

Electrolysis does not replace lost iron on the piece you are restoring! You are are reducing Fe+III back to FE(0). You are not electroplating iron on to the surface.

The sacrificial anode is so named not because that steel is maggicaly deposited on the item being restored but because it is surrounded by hydrogen and oxygen gas. The electric potential of the power supply is what protects your item, and hastens the destruction of the sacrificical anode if it is made of a reactive material like mild steel.

Caution about using alloys and or stainless steel as sacrificial anode... The alloys such as chromium and other materials are released into the solution
These metals are extremely toxic and extreme care should be used when handling. ESPECIALLY if you are reusing the caustic solution. and allowing the waste metals to accumulate. Do not just throw this solution away in your yard or down the drain. Using just mild steel or an inert material will not create a toxic solution. It will remain just water with caustic pH.

Carbon or other inert anodes (Platinum/gold) can be used if you are REALLY worried about consuming the anodes but really, mild steel is cheap and plentifull

Restoration electrolysys should be done at a rate of approx 1mA/square inch of surface area of the material to be restored. As the author of the article mentiones, if higher rates are used you risk blasting off rust from the item and losing iron that will be lost forever and producing a very uneven and porous iron surface that will rust like a S.O.B. if exposed to the elements again! It can also form that rippling and dimpling effect of uneven iron conversion.

Oh yeah if the item you are restoring has been recovered from salt water the salts need to be leached out first before you use electrolysis. I have soaked steel items in the toilet tank for 6 months. LOL That way you dont forget to change the water and getrid of the chlorides that are leached out.

Too much current produces excessive rates of Hydrogen and oxygen gas production. A very dangerous and explosive situation. High current rates also increase the risk of accidently creating a spark!

Only enough caustic material should be added to the water to make it conductive for low current flow. As rust is converted to iron, current will increase. As hydrogen and oxygen gas are produced, the water content will decrease and it will become more caustic and you guessed it...current will increase.

Mention has also been made of rhubarb leaves and oxalic acid as a rust remover. They are basically the same thing. Note oxalic acid is very toxic. That is why your grandma always told you not to eat the rhubarb leaves!

Oxalic acid reduces rust (Fe+III) which is not water soluble to Fe+II which is water soluble. Rusted iron treated this way literally lets you wash the rust away but as the name (rust removal) suggests this removes iron from the item you are restoring.

Electrolysis, conversts rust (which is Fe2o3) back to iron Fe and if no iron has been lost through leaching or mecanical cleaning should be restored back to its original shape if done slowly and in a controlled manner.

There really is nothing magical about the process and a stable, usable restored object can be obtained.

Oh and if the link to the article is removed send me an email and I will forward it to you.

Good Luck!

[Ralph Volkert]

Ooops I forgot to mention...If degreasing or paint stripping is your goal then do that. But that strength of solution is really too strong for an electrolysis solution to restore and conserve an item. It will not not only conduct current it will REALLY conduct a LOT of dangerous current unneccessarily.

[Bob Moseley (RIP)]

Morning Ralph (here at least) - Andrew Westacott's article on his site on this subject has certainly demistifyed the whole procedure for me. In fact eminating from that I will be changing some of my procedures and building a more efficient and safer de-ruster.

And as a general comment, here with Ralph, we have an expert in another field, namely science, upon whom we can draw advice from. Move over Wikipedia.

Bob

[maple_leaf_eh]

Originally Posted by Ralph Volkert

...

Caution about using alloys and or stainless steel as sacrificial anode... The alloys such as chromium and other materials are released into the solution
These metals are extremely toxic and extreme care should be used when handling. ESPECIALLY if you are reusing the caustic solution. and allowing the waste metals to accumulate. Do not just throw this solution away in your yard or down the drain. Using just mild steel or an inert material will not create a toxic solution. It will remain just water with caustic pH.

I've read this thread end to end and find the chemistry of the simplest things fascinating. But, I read all these chemicals and acids and solutions mentioned without much discussion of disposal. Bob warned about splashing your clothes, hands and eyes. Another fellow damn near blew himself up with a hydrogen gas arc! So, what happens to the immersion bath after the part is clean? Do you guys pour it out on the ground, down a sewer or neutralize it with the opposing Ph agent? Inquiring minds want to know.

[Bob Carriere]

.....Yes Terry if splashed you wind up with very holy pants and shirt sleeves.

Solution is to splash clean water immediately thenit only bleaches the pants.

The caustic solution realy removes the grease on your hands..... along with disolving a layer of skin.

Parts, after derusting were pressure washed in the gravel driveway.... keeps the grass from invading the driveway.

45 gallon drum of caustic solution was dumped on the ground near the barn on a particular heavy rainny day....... no bald squirrels were observed in the following days...... some dandy lions took a nose dive.

We always did our work outside so hydrogen was never a problem.... the hydogen sulphide released by the Rotters was far more offensive.

We also sand blast old, I assume lead paint, CMP paint and the sand does collect extensively in front of the barn. In certain areas like Phil in NH, who is next to a water reservoir, his expended sand has to be contained as a toxic substance and disposed in a special site.

So far things have been very casual in Hammond.

The strange behaviour of the Rotters may be a symptoms of lead posioning...

BooBee

[Ralph Volkert]

Hey Terry

I didnt mean to scare anyone. In the past I have never had to dispose of more than 1-2 gallons of elecrolyte. But I have never had a carrier before either.

Bob mentioned a good point. Have a good source of clean fresh water handy in case you splash any solution on your self or your eyes!.

My solutions never have any heavy metals from using galvinised or stainless steel anodes,etc so that has never been a concern for me. I only use enough sodium hydroxide to get conductivity so yes it is caustic but probly no more and probably much less than an automatic dishwasher load uses. So I have usually disposed of it down the kitchen sink drain with lots of running water. Still it is less caustic than a drain cleaner but still works well to help keep the drain clean!

If you dumped it outside and was very strong solution you probly would be killing grass and weeds but the soil should neutralize it fairly readily.

The problem is with heavy metals. If that is in your solution and you pour it on the ground, it can get in to your garden or when it dries the dust can go airborne. I am an old Fart anyway so I am not too concerned about myself but the grand kids and nieghbour kids I worry about.

The caustic electrolye itself is not a big deal if that is all it is. But if you don't know what you are doing neutralizing it can cause other issues. It can get very hot. (hydrochloic acid or bleach mixed with it may generate chlorine gas and a wiff of that will REALLY clean out your sinuses and lungs!) So as Bob suggested, if all it is sodium hydroxide, wash soda etc judicious disposal is not a problem. (In other words don't water your wife's roses with it!)

Just remember, all you are making is a strong detergent solution. ie similar to what you use in your automatic dishwasher. Just remember if it is paint stripper bath strength you may want to dispose of it slowly because it is so strong!

When I make up a batch, I know I will be using it for some time so I just cover it up and store it in the basement or the garage for the next time. But it is also great for cleaning oil stains on the Garage floor, rags etc. So around my place it has never been around too long any way.

[Phill]

Brought this thread back to add this link from 'Shop Floor Talk'. Phil
http://www.shopfloortalk.com/forums/...ead.php?t=1695