[Ultralow787]

Hey guys, I have seen Jody mention "Nitral" and there are all kinds of references on the web to using Nitric Acid to etch the cross section of welds. Where can you easily get this stuff?
Is there a commercially available solution through welding supply houses to do this?

We just want to be able to see the penetration on mild steel welds.
Thanks

[Fat Bob]

Nitric can be a bit hard to get in the US but Naval Jelly (phosphoric acid) from any hardware store works. Just cut, polish and smear some on. Wait 5-10 minutes and wash it off, your weld will be darkened...

[zigeuner]

Phosphoric acid is available from most any chemical supply warehouse. I use it in my shop from time to time to remove surface rust and to pickle clean metal. I pay about $20 for a gallon of 70% phosphoric acid. The same place that sells phosphoric also has any other acid you might want, although if you can use phosphoric, it's much nicer to work with than nitric acid.

Always pour acid into water to dilute rather than the other way around. As with any other acid, eye protection, rubber gloves, good shoes, long sleeved shirts and full length trousers and so on are needed.

[Ultralow787]

Thanks Guys!
I did find some "pickling paste" at our local welding supplier. It is quite pricey at $108.00 per half gallon though. Naval Jelly used to be common around here, but not so these days. I used to use it to kill rust on car bodies.

[Otto Nobedder]

Your local paint supplier might have "OsPho" or similar, a medium strength phosphoric acid for rust conversion.

Same principle as naval jelly, but a water-thin liquid.

Bought my last from Sherwin-Williams.

Steve S

[Ultralow787]

Thanks Steve,
I ended up picking up the "pickling paste" today. The stuff works awesome! It is almost instantaneous. The container says it is Nitric acid and Hydrofluoric acid. I now have more than I could ever use!

[Otto Nobedder]

Post up some pics of your etched welds!

Steve S

[Otto Nobedder]

Sell small quantities?

Many here have shown interest!

[offgridqld]

The pickling past sure dose work well (don't breath the fumes in and watch the eyes its nasty stuff) I also got a shock when I purchased my 1st bottle as its not cheap but it lasts for a long time.I moved state a few years ago and the moving company refused to ship it so I gave my bottle to a friend. I have been looking into buying a electronic weld passivation machine. Again a bit of a investment but amazing results on stainless steel. A lot safer than pickling past. At work we had to go though all kinds of hassle about the safety of using pickling past on SS in a food processing plant. Especially inside a closed space like a mixer or CIP tank with all the fumes and also were the stuff ended up after wash down.

Has anyone had experience with the electroplolishing weld passivation machines as I might bite the bullet soon and get one.

Was look at this one local manufacturer for me http://www.metalscience.com.au/machine_TIG_Champ.htm There is a few good videos on there that show how well they work.

Kurt

[noddybrian]

it's funny you should mention that Kurt - but I was going to post some pics soon on the " redneck " version - I saw a product sold in here in the UK called "Tig Mop " but it's like 2K which seems over the top for home use - different in a production job - so I kept trawling on the internet & discovered several others - the process seems so simple I tried it & got quite good results - if the welds are just coloured it works instantly - if you got hung up or had bad fit up on thin gauge & cooked a bit till black it takes longer - still experimenting but will post pictures when sorted.

The process appears to be electolysis using dilute phosphoric acid as the electrolyte - though as this is used to clean stainless I guess there is also a chemical reaction with the surface - I'm using an unknown strength acid sold for cleaning aluminum truck bodies ( £15 per gallon ) this is diluted & I've found 1 part acid to 4 of water quite sufficient.

From what I discovered the commercial " clean only " set uses about 30volts AC & up to 80 amps depending on size of applicator & degree of cleaning required. The "clean & polish" sets ( not really what I'd call polished though ) use 25volts DC & the same current range - some use a brush with conductive ( I think carbon fibre ) bristles - one I saw which was Australian used felt pads - the only requirements are it needs to absorb / hold an amount of fluid & be fairly tolerant of temperature as a fair bit of heat is developed - the brush type eats the brushes away quite fast & are not easy to find except from the manufacturer - either type leaves a small amount of wet residue that needs washing off and / or neutralising with a weak alkali like baking soda.

On my first play I got a 1-1/2" square of about 3/32" stainless sheet welded to a piece of 3/16 rod about 6" long ( looks like a lolly pop ! ) I have some rubber fuel hose over the rod to insulate it from accidental earthing except the last inch which goes in a regular rod holder - around this & retained by an " O " ring I'm using 2" wide high teperature exhaust tape ( looks like woven asbestos ) available real cheap from local boat supply - for a power source I'm using the worlds oldest air cooled " buzz box " as this welder only puts out 40volts - this is probably a bit high so I'm about to put leads into a 24 volt battery charger I've got laying around - these put out at least 28 volt DC so if you go straight to the transformer allowing for loss across the rectifier I'd expect 30 to 32 volts - this should be fine - just power up, dip pad in acid & gently agitate on job - colour goes almost instant & you don't need to worry about that nasty pickling acid - ( is'nt that like "Alien" blood ! ) I used this recently on a stainless gantry frame I made for a fishing boat & was pleased with the results - most of my stainless work is polished so except in tight corners it all comes off with the wheel - but this thing was all brushed finish like your furniture - I did blend some bits with a " Scotchbrite " wheel.

As to acid availability - in the UK nitric is on a list of controlled substances by the government due to needing it for almost all homebrew primary explosives - but on Ebay just look for " gold testing kit " - just tell them how many litres of " testing kit " you require !!!!! you got to love Ebay.

Got to say Kurt I love your power solution - but am I the only one severely dissapointed - when you say " melting metal with the power of the sun " I was hoping to see a massive array of parabolic mirrors all focused into some sort of " death ray " aimed into a furnace - or like the one on James Bond - Man with a golden gun !!!!!!!!!!!!
All the best.

[weldin mike 27]

Hey,

Ah ha, the good old death ray. This is why I love this site.

Mick

[offgridqld]

Putting together a battery between between 20 - 50 volts that can handle up to 80 - 100A output isn't to hard. Would have to think about ways to control the amperage it gives off though but wouldn't be to hard. I do have my old Esseti 160A inverter Tig /MMA unit that I could play with as a power supply

Searching on ebay I can see some units sold locally for $1000 (though they have make an offer next to them so perhaps a little less) One seller offers testing of unit before purchase.

less expensive ebay unit
http://www.ebay.com.au/itm/500WATT-STAI ... 4ac16e0269

With my old old scratch start machine using stock ceramic cups and working in carport style work area with no walls . It was like ...Quick weld before the wind blows the Argon away . So I got some discoloration on the welds not much black more just a gold - rainbow and perhaps a tad of black surface soot where the small ceramic cup didnt cover wide enough. Usually a dark spot at the very end of each weld as you have to pull the torch away with a quick flick (being scratch start) and you loose your gas coverage at the very end. The top and sides was all polished out t so no issue it was just the underside .

Now I have a 1300ft2 workshop at home to work in (with walls so no wind blowing gas away ) A new machine with with HF start and post gas flow along with looking into some gas lenses and much larger cups I should be able to avoided a lot of the cleaning. That said some light cleaning to just restore the surface and limit tea staining over time will still be necessary especially when sold to some one who lives by the ocean.

Kurt

[noddybrian]

It does seem the UK is very badly served by the weld supply industry or at least in my area - most stuff that Jody uses is not available or costs stupid money - we can't even get the CK flex loc torches or stubby gas lense kit here.
Anyhow the only weld cleaner sold here is in link below.

http://www.ebay.co.uk/itm/TIG-MOP-WELD- ... 35b950e954

advert contains a video - but just in case here's the link
http://www.youtube.com/watch?v=R2-v05hnGX0

While looking around to find out more info I also found this one which gave more details.

http://www.youtube.com/watch?feature=en ... reZEI&NR=1

Hope this helps your research .

[offgridqld]

For $2000 in the UK Actual about $4000 AU or US is a lot of $ just to clean welds. You could buy a lot of scotch pads and pickling past and pay a very enthusiastic 15yo kid for a long time with that kind of money

Honestly cleaning up welds is one of my pet hates. I could see the value on big jobs and the finish looks better than pickling past. Looking at the sum of parts VS the cost. A basic DC inverter tig welders can be purchased for under $500 now days. I'm sure the weld cleaners wouldn't cost any more to build . Must be a supply and demand thing.

Kurt