Rust on stainless welds

[Rob55]

I recently received some stainless pipework for an agricultural slurry store which was fabricated by an engineering company. I have noticed the welds are now starting to go rusty and am concerned that this will lead to failure given the extremely corrosive nature of slurry.

Can anyone tell by these photos what has gone wrong and whether I should reject the work. The components have already been fitted and are immersed in slurry so it's not an easy job getting them replaced.!

 

[Rocketman]

What grade of stainless you using/specified. I would have thought if it is a highly corrosive environment it would be 316L and so would have used a 316L tig filler rod.

 

[Gavin_d]

Looks bad. Either stainless filler wasn't used or it's been cleaned with a wire brush contaminated with carbon steel deposits. You could try cleaning the rust of with a stainless steel wire brush and see how it cleans up. If it's very shiny then stainless rod was used but if it's dull and soon rusts again then it's either contaminated or non stainless filler was used. To be honest I would contact the company that made them.

 

[Bill Edwards]

I think it has been welded with 'ordinary' (i.e steel) filler metal, rather than stainless which should be used.

I guess somebody welding it didn't know, bother or remember and just got stuck in as thought welding steel.

To me the rust looks quite bad really, I'd be unhappy with that work as it will shorten the life of the system/part.

 

[TechnicAl]

I have to agree it certainly looks like they used mild steel weld metal

Are they stainless bolts?

 

[edd]

They are galv bolts.
I would guess at the wrong filler.

Back to the supplier with that one, coated in as much slurry as you can.

 

[Rocketman]

They are galv bolts.
I would guess at the wrong filler.

Back to the supplier with that one, coated in as much slurry as you can.

Yeah the 8.8 is the big give away on the bolts.

The cap heads might be stainless but without seeing what it says on the head who knows.

 

[baconbarm]

That's got to be m/s filler rods for me.

It looks like rust is starting from the weld, then spreading outwards. Its too severe and constant to be from a mild steel wire brush or a tainted grinding disk.

 

[hotrodder]

2nd pic right at the top there's a small portion of weld that isn't rusty. Maybe it's the pic (or me) but it doesn't look like mild steel... the colour's wrong, there's rust at the toes of the weld (and what looks like cold lap) but the bead itself is brighter with less of a blue-grayish hue than typical for carbon steel
Either way the numpties that made it have managed to FUBAR it and contaminate the pipe and flange with iron well away from the welds too

 

[Paul.]

Hard to tell whats really going on from a picture, but looking at the contamination on the edge of the flange well away from the weld I would suspect that its been cleaned with an ordinary steel rotary wire brush, Have seen something similar happen when a steel wire cup brush was incorrectly supplied as stainless.
Re brushing with a stainless brush then use pickling paste to re passivate may cure it, I would also be concerned about the inside of the joint if its had the same treatment.
The welding doesn't look that good anyway, I would just reject it.

 

[backpurge]

If the rust was just just on the weld and immediate parent material I would initially suspect the surface oxides (colour tints) had not been properly removed after welding, however when you see the random patches of rust in various places I think this is pointing more to contamination from something like a mild steel wire brush, either way the fabricator needs to make it right otherwise the component will eventually fail

 

[norlander]

I had a piece of scrap "stainless" sheet. I cut out the word "stainless" when playing with my new plasma cutter. I left the off cut outside. It went rusty. I just assumed that the heat had knocked out the Cr composition or whatever it is that makes stainless stainless.
But that does not make sense because stainless zorst systems on motorcycles have flanges welded on them and they do not rust like that from my memory of having bikes with s/less systems and they are exposed to the elements and heat fluctuations.
A complete supposition, based on no knowledge whatsoever, led me to guess that in todays market, there is quality stainless and lesser quality stainless.The stainless I cut was from a DIY shed.
That might apply to the quality of the filler rods as well?.

 

[langy]

Not all flavours of stainless are actually stainless !!! I would be sending it back

 

[langy]

I had a piece of scrap "stainless" sheet. I cut out the word "stainless" when playing with my new plasma cutter. I left the off cut outside. It went rusty. I just assumed that the heat had knocked out the Cr composition or whatever it is that makes stainless stainless.
But that does not make sense because stainless zorst systems on motorcycles have flanges welded on them and they do not rust like that from my memory of having bikes with s/less systems and they are exposed to the elements and heat fluctuations.
A complete supposition, based on no knowledge whatsoever, led me to guess that in todays market, there is quality stainless and lesser quality stainless.The stainless I cut was from a DIY shed.
That might apply to the quality of the filler rods as well?.

I only use 316 or sometimes 304, the other grades can corrode quite badly very quickly

 

[Kent]

Gosh I was expecting a little staining! send it back. If I had to guess I should say a std wire wheel in an angle grinder did that as I can see were the user left side scuffs and were he didn't need to hit so hard. The bead looks a little iffy in places anyhow

 

[Richard.]

The rust looks to of extended quite wide on to the pipe it self in areas so I'd rule out filler and surface oxide. I'd hazard a guess and go with the majority on contamination. Perhaps there was surface oxides at one point which may have been the reason the welder used a contaminated abrasive to try and clean them off but obviously made it a lot worse.

 

[Richard.]

You can even see it on the square edges of the flange where I would guess the wire brush/cup has caught it there.

 

[Mr shiney]

Ha! I have done exactly the same thing on a project recently. I am a hobby welder not a fabricator so have an excuse for stupidity!!

I made a rod holder by welding a piece of pipe onto some flat plate in almost exactly the way that flange is made. I thought I would polish the welds up a little to give it a nice finish. I used what I thought was a brass wire wheel which is actually just a brass coating on steel wire. It looked lovely for about a week and then I ran the propane heater in the garage which the ran out of gas which leaves a very light condensation on everything. Came back the next day and the welds looked identical to that!!!!

While we are at it, whats the best way to clean them up?

 

[langy]

I was doing a job once and ran out of 2.5" 316 round bar, only needed 2" to finish and knew my mate had some so got a bit off him, machined and polished it and put it on the car, looked at it 3 days later and it was covered in rust !!!

 

[Rocketman]

I only use 316 or sometimes 304, the other grades can corrode quite badly very quickly

Other grades - trouble is back in the early 90's when I was doing a course on stainless even then there were over 100 different recognised grades with different attributes. Like you say for easy life just go with 316 / 316L in highly corrosive environments for fabrication work.