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Swarf&Sparks
08-13-2008, 10:45 AM
Saw something interesting on the idiot box tonight. (for a change)
Anybody out there that welds stainless will appreciate this.
Yes, you can do it in a tank, or with hydrofluoric gel, or mechanical methods; but I reckon this guy could be on a winner.

http://www.abc.net.au/tv/newinventors/txt/s2324925.htm

Scishopguy
08-13-2008, 12:45 PM
I used to work in the Oceanography Department at Florida State University and had to build many bits of hardware used to moor instruments in the ocean. We typically used type 316 stainless stock and ordered nuts and bolts made of the same alloy. We found that the stuff would get surface rust that would let the corrosion process get started unless we passivated the parts. The safest and easiest process for this is to soak the parts in a mixture of phosphoric and oxalic acids, commonly found as a commercial rusty metal primer called "Ospho." One of the faculty needed convincing that this would work so I took two beakers with a handfull of 3/8" 316 bolts and soaked one of them in Ospho over night. I rinsed them both in tap water and then filled both beakers with sea water. I put them on his desk and that is where they stayed for 2 weeks. The untreated bolts began to have little streaks of brown while the treated ones were just as bright and shiney as new. I would much preferr this treatment to hydroflouric as HF is so nasty and dangerous. The Ospho is not a strong mixture and does not burn you but should be washed off immediately, as with all acids, if splashed on the skin.

Good luck with your project

Swarf&Sparks
08-13-2008, 01:11 PM
Jim, did you bother to have a look at the vid link?
this is a new approach to electro-chemical passivation.

Much of my work has been marine stainless.
And I would not put a 316 nut on a 316 bolt/stud!
304 or 308 nuts on 316 bolts (or vice versa) are unlikely to gall and sieze.
316 on 316 is likely to seize immediately.

And, yes, I've used HF gel and all the other methods.

Ries
08-13-2008, 01:11 PM
This type of machine has been commercially available for at least 20 years. Maybe in Australia this is a breakthrough, but I have a less sophisticated commercial unit I bought around ten years ago, and I now use citric acid, rather than the nasty looking red stuff he shows, and its even less dangerous. The citric acid I use wipes off with wet rags, and doesnt burn holes in your jeans.
Here are two sort of clumsy american models, both of which are expensive for what they are, and not as cool looking as the new Aussie model, but which work just fine, and have been in use commercially all over the USA for many years.
http://www.weldprousa.com/
http://www.screenpro.net/

I buy Citri-surf in powder form, and mix it up as needed. Its cheaper, safer, and easier to deal with than Ospho or other acids. Oshpo is a phosphoric acid, which is what is in Coca Cola.
http://www.stellarsolutions.net/


Here in the USA, and in Europe, the best model of this type of machine is made by Walter, and it looks like he has copied several of Walter's unique features- I am amazed Walter didnt have them patented in Oz.
The only new feature I see in his unit is the water pump cooling the torch, which, frankly, I dont see a need for- the heat on my unit is not excessive, and its one more expensive and complicated system to maintain.

Here is a link to the Walter machine- its called a "Surf-ox" and Walter has been selling em in europe for probably close to 20 years.
http://www.jwalterinc.com/walter_us/servlet/ProdSummary?franchise=surfox&criteria=prod&category=126&cbopgroup=127

Swarf&Sparks
08-13-2008, 01:18 PM
Thanks for that Ries.
If you think he's "Copied" anything, I suggest you inform Walter. :rolleyes:

Ries
08-13-2008, 01:27 PM
I am sure Walter can look after themselves.
The system of slip on white absorbent fiber covers, though, is something Walter probably does have patented.

The basic electrical circuit is so simple, I am sure its not patentable- many people just use battery chargers for this purpose, although the purpose built machines are usually 40 volts.

By the way- it works, great.
I have electropolished thousands of welds in Stainless over the years with mine, usually in 304, but occasionally 316, and it does a great job at it.
I do a lot of heavily forged stainless steel work, though, and a small portable unit like this will not take the black off that forging produces- for that, I send it out to a commercial electropolishing company, which uses phosphoric/nitric acid mixes, heated to 120 degrees farenheit, and a 1000 amp power supply to really strip em clean.

This fence, for example, is 320 linear feet long, made from 1/2" round stainless bars that were heavily forged, then scrolled. I had to send them out for shop polishing, but then, on site, the 8 foot long sections were welded together, and all site welds were electropolished with a portable unit like the one shown, and the welds blend right in with the rest of the piece. In this photo, you can see some welds that are yet to be electropolished, but when I was done, they are invisible.
http://img.photobucket.com/albums/v132/rniemi/phx014.jpg

Scishopguy
08-13-2008, 02:21 PM
Jim, did you bother to have a look at the vid link?
this is a new approach to electro-chemical passivation.

Much of my work has been marine stainless.
And I would not put a 316 nut on a 316 bolt/stud!
304 or 308 nuts on 316 bolts (or vice versa) are unlikely to gall and sieze.
316 on 316 is likely to seize immediately.

And, yes, I've used HF gel and all the other methods.

We put salt water proof grease on all of our threaded stainless parts before deployment and seldom had trouble removing them. In the early (learning) days we had trouble with crevise corrosion but the grease seemed to stop all that. We tried silicon grease and that worked but was not a good lube for threads.

As for the HF, we all use what we got and what works for us. They had lots of HF around the labs at work and they always stressed the dangers of any exposure to it and what it did to your bones. Prolly a barrister at the bottom of it all but worth a listen just the same. :)

As for the video, I don't have much luck with my dial up connection so Utube and some others are not often looked at. Things will be better when I can drop the Tallahassee Florida bit from my sig line.:(

best regards

Swarf&Sparks
08-13-2008, 02:28 PM
Fair nuff Jim, I used to suffer the dial-up too :(


Ries, you've just answered your own criticism
"phosphoric/nitric acid mixes, heated to 120 degrees farenheit, and a 1000 amp power supply to really strip em clean."

And you wonder why the cooling? He's also using dilute phosphoric.
You drink that if you're into ***cola.

Ries
08-13-2008, 04:56 PM
I am not criticising- I am just pointing out that his system is nothing new.
And his system, as shown, is not in any way a replacement for the heated acid bath with 1000 amp power supply.
It is a touchup system for cleaning welds.
Just like the three I showed.

This type of system works great for that purpose- cleaning the discoloration from welds.

It will not polish large areas, especially if they are discolored from forging, or they are dull mill scale, or sandblasted, or other types of finish that require actual tank electropolishing.

The site polishing rig is an indispensable part of my business- I am not putting it down- its just not the magic bullet for all problems, nor is it something new.

mwechtal
08-13-2008, 10:22 PM
As for the HF, we all use what we got and what works for us. They had lots of HF around the labs at work and they always stressed the dangers of any exposure to it and what it did to your bones. Prolly a barrister at the bottom of it all but worth a listen just the same. :)

best regards

No, it's not just the barristers, HF really is nasty stuff. It will do a lot of damage to your bones, and by the time you feel it it's already done most of the damage. Any chemist will tell you the same thing. Amateurs really don't have the training or equipment to deal with it safely. Acids that people think are really nasty like Sulphuric or Nitric at least have the decency to hurt when you get splashed.

wierdscience
08-14-2008, 12:49 AM
I first saw similr being done copper plating actually about 20 years ago,setup was simple,but expensive.

Done a lot of marine stainless,most of it undewater.A lot of the oilfield work we have done has been speced marine anti-fouling coating instead of passivation.Gypsy barnacles will stick to 316 quiet nicely turns out and the fouling paint prevents it.

Best anti-sieze for long term saltwater use is pine tar.It doesn't wash off,ever and is impervious to infiltration.

Evan
08-14-2008, 01:19 AM
What Mike said. I have used HF acid too and the problem is that it soaks in through the skin without any warning. It's very slow acting but it cause very serious and very deep burns. It kills the tissue right to the bone and takes apart the bones too. If you have any significant exposure that isn't properly treated the usual remedy is amputation. If you get treatement soon enough after a skin exposure they can carefully shift your body's acid/base balance enough toward basic to neutralize the acid.

Swarf&Sparks
08-14-2008, 06:23 AM
Agree and then some, re all said about HF. It's a BITCH!

I've worked with it under many guises. SS welding, glass etching, and on the hydrofiner at an oil refinery/chem plant.

Calcium tabs, gel, and IVs are standard issue, along with spacesuit type PE.

Please, do not treat it lightly, even in 1% or 3% gel form.