[hotspanner39]

Hi,When tig welding stainless, can anyone give any advice on preventing "Coking" on the back of the weld apart from back purging?
Thanks in advance..

[WTFH]

By coking I am assuming you mean sugaring. Since purging can be somewhat of a pain at times when I can I'll put a piece of aluminum on the back side of the joint to protect it from the atmosphere.

[noddybrian]

Only thing that regularly crops up as an alternative to back purge is " Solar Flux Type B " - it seems it's not badly priced stateside though is expensive here - maybe worth a try - obviously you need to be able to apply it to the relevant part prior to welding - don't know if this is practical for your application - it's on Ebay if you can't find it locally.

[Braehill]

I seen an Aluminum tape that was made for backing up welds on stainless but I don't remember what the name brand was or where I saw it. Sorry, memory is the first thing to go.

Len

[Adam's Got Skills]

I was wanting to buy some of that aluminum tape too...That's what I've seen mostly as a go to instead of back purge. But it is stupid expensive! It's basically a strip of aluminum with an adhesive on the outside edges only....I saw a 75ft roll and asked how much it was...They said 75$ for a 25' roll so there for 75' yeah I ain't got the bank roll like that right now...I wonder if you could use just aluminum foil or something??? Idk how you'd get it to stick tho I'm sure it'd have to be some kind of special adhesive to not burn all to hell. I now I'd like to figure something out too, but I don't do enough stainless projects in my garage to justify paying 200 bucks on freaking rolled aluminum foil with glue on the edges

[Markus]

Picture would help a lot

Flux is a good choice sometimes. Better than tape, but it's not same as purging at all. It all depends what your product need to stand. If it goes to corrosive environment then good back purge is a necessity!

[Artie F. Emm]

Try a google search on "foil HVAC tape", or check out this link at Home Deep: aluminum, $4 for about 10 yards. Would this do the trick?
http://www.homedepot.com/p/Nashua-Tape- ... ifications

I recall one of Jody's videos featured a tape that was sticky only on the edges to avoid getting glue caught up in the weld.

[Braehill]

If the HVAC tape is 2" wide, you could fold a peice in half and run the folded peice down the middle of another peice so you would have 1/2" exposed on each side to make it stick. The glue would be contained in the fold and you could leave an air gap in the middle behind the weld to trap the Argon. Haven't tried it but I think it would work and at the price it would be worth a try.

Len

[kiwi2wheels]

Depending how close your weld is to the adhesive, this can sometimes be useful, also if you use in conjunction with heavy aluminum kitchen foil to make a gas dam.

http://solutions.3m.com/wps/portal/3M/e ... 115&rt=rud

[hotspanner39]

Thanks very much chaps, some interesting tips there, I'll have to have a dabble

[weldin mike 27]

Hey,

There is product called TGX which is fluxcored tig wire. Its made for finishing piping systems that cannot have the last weld purged. Its a serious product, expensive, but it would be handy to have a bit around for the odd job.

Mick

[TamJeff]

Make a purge plate and weld it reverse travel, so that the gas drenches the puddle until it's frozen and beyond.