[welderkid556]

hello, i have a question about acid etching and cleaning steel with muriatic acid. i just started using muriatic acid to strip old metals of rust before i weld them and it seems to work well. my question is after the acid has removed the heavy rust and i spray it with water to remove the acid, whats the best way to stop the clean metal from rusting again?

my 2nd question is about acid etching steel to see the weld nugget. i watched a video that jody did and it was a coupon he did acid etching on, it was short circuit mig and spray transfer and he used a sort of acid to see the weld nugget. i was wondering what sort of acid it was, im wondering if it was the same acid ive been useing.

[Otto Nobedder]

Etching with muriatic acid can be done, but it's recommended to be at "boiling" temperature, and the fumes are potentially deadly, so it's usually done under a fume hood.

I recently read an article on the subject, that offered several etching formulae for various metals. I'll look in my browser history, and post the link if I can find it.

As for protecting metal from rust after acid cleaning, I'd recommend washing the parts with baking soda/water to neutralize any leftover acid in pores, a water rinse, blow it dry, and then a thorough coat of an oil-based anti-spatter spray. It can also be painted with "weld-through" primer. This stuff is suitable for stick, fluxcore, and dual-shield.

Here's an example:

http://www.tcpglobal.com/spraypaintdepo ... imers.aspx

Steve S

[Otto Nobedder]

Here's a short article on etching, though not the one I referred to:

http://www.mig-welding.co.uk/wiki/Macro_Etch

Steve S

[Otto Nobedder]

This also is not the one I read, but is actually more thorough:

http://www.eng-tips.com/faqs.cfm?fid=1111

Steve S

[welderkid556]

thank you for the help.im starting on this 3rd tower now and i welded a peice of 4 inch pipe to the plate that holds the entire tower down. theres a hole big enough in the plate that the pipe slides through it. i have 2 feet sticking through the bottom and 3 feet on top. i used spray transfer with solid wire today and it seemed to work pretty well at the right setting. but i tried to turn the heat up another 2 notches for the mid range heat and turned the wire up and it seems to make a popping sound and makes porosity. if i turn the heat down 2 notches to where the machine reccomends it, it works fine and sprays in like a river. so if i just turn up the heat and not the wire speed possibly that would make it settle down? i have some more welding to do on this plate on the bottom side so i can try any idea on the back side where it still needs welded.

after this tower base is finished we will start welding the tubes together with the flux core wire for outside use. thank you for all of your help and technical support, much appreciated bud.

[Otto Nobedder]

Spray-arc is not my forte', but I know that if you dial up the volts and don't match it right with the wire speed, you'll erode the tip in a hurry. The popping you described, with accomanying porosity, may in fact be tip overheat pulling copper from the tip into the puddle.

This is just speculation.

Hopefully, someone with real spray-arc experience will comment.

Steve S

[welderkid556]

i checked the tip on the gun and its pretty clean and not much on it except a little spatter. im going to do some experimenting tomorrow morning and see how hot i can crank it untill it becomes very fluid in the puddle perspective. practice makes perfect. but i thought of another possible problem. the argon co2 gas . i just got a refill, i read up on the subject, and spray transfer is suppose to be used with 90/10% argon, co2. and im useing 75/25 argon co2. maybe thats why its not reacting correctly to the high voltage.

[Otto Nobedder]

That would make a lot of sense... I hadn't asked about the gas in the equation. I've seen spray-arc gasses from 90/10, to 98/2, with the "2" being oxygen. With no real experience in it myself, though, I'll defer to those who know what they're talking about. I'm sure one will come along shortly...

Steve S

[rake]

It's been years but we sprayed a lot in the shipyard. No bacon. Should be a hiss.
We ran .045 and 1/16" wire. (we ran 80S and 100S) 28-32v and wire speeds around 700 IPM
We ran 90-10 also.
If you're getting spatter and porosity try turning down your volts and wire speed a little.
If you're heat input is too high the puddle just can't handle it and the cheeze will appear.

Remember, hisssssssssssssssssssssssssssssssssss.

[welderkid556]

hello, i did some more welding on some 3/4 inch plate and i found a happy medium setting. i just had a refill of 75/25 because thats all i could get here in town but i will go buy a new secondary tank soon out of town and i will get 90/10. not many people in this area do much spraying except for about 1 other company in the area and me and the other company is an industrial shop building tanks for caterpillar offroad trucks for mineing and such and they use stargon is what its called. i remember when i worked for them we had almost every type of mixed tank there was but mostly we used stargon and 90/10. i dont know what the contents of stargon but it seemed to spray a little nicer than 90/10 or maybe it was the settings of the different machines make it seem nicer between 1 miller to a lincoln but who knows. my machine is a airco dip pak 200 and i dont know how to learn all of my setting to compare to ipm for wire feed control and on the voltage im not sure, theres a course heat control that has low mid and high then then mid range fine tune heat goes from 1-8. i looked at the stamp on the machine and its rated output is 30 for the voltage but if i go too far up in heat setting the puddle looks like swiss cheese as you said with this gas mixture. i will just have to wait untill i can get my secondary tank to try. also, how much cfm should i be useing from the tank? if i have anything below 25 cfh i get porosity in every weld. if i turn it up to 35 im ok for getting clean welds. this is a brand new tank and i know im getting gas because ive tested this many times. do i need more cfh or is that messing with things and creating the porosity?

[Otto Nobedder]

The only comment I have, is that I use 30-35 cfh for all things MIG and dual-shield, and sometimes more when I can't control the draft.

Steve S

[welderkid556]

i do this solid wire and dual shield inside my shop with the doors closed and there are no drafts. that way there is no air being push near the area im welding or any air being pulled away. i usually do about 5 welds then open the shop door to air out the place. the smoke doesnt seem to bother me but my co-worker seems to caugh up a storm when i open the door lol. ill try to turn the cfh to between 30 and 35 and see what it gives me for shielding. i think im going to get yet 1 more size bigger for the gas nossle and see if them helps improve the appearance of the puddle. i did some experimenting with stickout today, if i hold the nossle and tip close to the puddle its beautiful. if i pull back to see what im doing it gets porosity. seems like a gas shielding problem to me still but thats my opinion. im thinking about buying a new mig gun and get away from this tweco gun, best luck ive had were the bernard guns that were on the millers i used at my old job and i believe they had the 3/4 inch gas nossles and i never had any problem with those guns giving me bad welds unless it was windy outside and the co-worker opened the door next to me. im going to take a look and see if i can find a bernard gun that will fit my machine.

[noddybrian]

Hi - I do a fair bit of spray transfer on backhoe buckets & other construction machinery - in the UK BOC has a virtual monolopy on welding gases & don't do exactly the same mixes as I'm reading about on the forum which is mostly USA based - but for spray transfer / heavy Mig welds ( they say 10mm & above ) they recommend & supply 80 / 20 ( roughly - as there's a bit of O2 in it as well ) so I doubt the mix is causing you the problem - I've never tried 90 / 10 as this is not used or available here - but we have 95 / 5 - this is not suitable for spray transfer / thick section or alot of amps. I do find though certain shape joints & sometimes the position when putting in alot of heat can cause a sort of thermal air current that disrupts the gas flow causing similar problems to yours -the more heat the worse it is - obviouly the longer the stick out the worse this is & upping the gas flow often won't help - gaps are especially bad - I often fill all fit up gaps with a lower power setting then let rip on the fill passes - I don't find a larger gas shroud helps & my old instructor hates them - always insisted on quite narrow tapered shrouds despite being on a large torch on a 500amp set - but from torch to torch the gas flow if you could see it varies - maybe by the diffuser design - I've always wondered how the gas usually remains where it's needed with Mig with such poor dispersion - it never seems to with Tig - maybe someone has / will invent a gas lens Mig shroud . Also there seems to be a finite maximum amps for a given wire size / material thickness - beyond this you get porosity issues - I think the pool gets too big or boils , dragging in air from the edges - so if you reach this point back off a bit - not sure about your set but here all the torches are connected with a quick release " Euro connector" this has a very fragile "O" ring to seal the gas - maybe worth checking this as I had one drag air in much as gas line leaks on Tig sets do. - best of luck with your project.

[Otto Nobedder]

Has anyone tried packing stainless steel-wool around the diffuser on MIG? This trick works well on TIG when a standard collet and cup is all you can fit into a tight joint... It diffuses the gas somewhat like a gas lens.

The down side is that this defeats the insulator, and if you touch the nozzle to the work, it will short.

It wouldn't be cheap, but a ceramic nozzle, or hybrid nozzle with a built-in diffuser... Hmmm. I've got to give this some thought.

I haven't done a MIG weld in two months at work, but the next time it comes up, I might give this a go and see how low I can set the gas flow.

Steve S

[welderkid556]

hey guys and girls, if there are any girls, welcome. this 90/10 gas mix is working beautiful, nice smooth arc and beautiful. but i was wondering, i now have 3 tanks. one tank is 75/25 ar/co2 for my 220 airco mig, the second tank is 90/10 ar/co2 also for my 220 mig, and for aluminum on my tig rig i have 100% argon. now my question is how does co2 affect or do anything for welding and the same for argon. in a mix tank does argon cool the puddle to a certain degree and does co2 heat up the puddle? i use to use straight co2 on my small hobart long ago and it was very hot even in a 110 machine which is good for penetration but the looks of the welds werent too pretty or up to my standard anyways. i use just the argon for tig. but at what point does the gas make the puddle turn from short circuit type of weld to spray? i mean like what percentage of gases does make it change the arc and puddle.with this 90/10 gas the ripples are almost non-existant. when i run 75/25 i get fine ripples. im still young and learning and i want to be the best i can. thank you for the replies, and future replies.