[Pants]

I've got some custom-manufactured 304 stainless tube posts for a handrail project that were fitted with unknown grade of stainless nuts spaced along the sides, intended to secure stainless wire-rope for more or less the standard cable-handrail look. But the fabricator used the wrong nut size (8mm vs 6mm)...AND they're noticeably rusty, after a few months of exposure while set aside, prior to grappling with the wrong-size-nut problem.
https://photos.app.goo.gl/aRD1YCZUucvJ1rR1A
I'm thinking about drilling the 8mm nuts out so as to preserve the centers (assuming there's enough meat left to center new 6mm nuts), then welding the new nuts in place - but what of all this rusty-looking crap? Nuts are SOME grade of stainless, not mild steel, but it's frustrating to have to fix these problems, and doubly so if the rusting continues later. It's all going to be quite exposed to the elements, including lots of rain.

[cj737]

If those are stainless, I’ll eat that handrail. Probably some type of zinc or cadmium plated nut that when welded, burned off the plating.

I’d drill them out completely, plug the hole with a new piece of round stock that is pre-tapped for 6mm. You’ll chase your tail and never have the finish you seek trying to “fix” that crap.

[tweake]

as above, probably plated steel nuts, tho i wonder about exhaust grade stainless which is barely considered stainless.
i wonder why they fitted nuts, its cheaper and quicker to just tap it.
as above i would remove the nuts completely, plug and tap.

[Arno]

Try sticking a magnet on the nuts. Likely they are highly magnetic and quite likely just plain (mild-)steel.

Could be 409 'stainless', which will definitely rust and is not suitable for these applications, but as it looks like it's even rusting inside the threads that seems unlikely.

Best option would be to drill these out completely, pickle the area to get any steel and rust contamination etched out, and then have some stainless threaded 'plugs' machined and then weld those in.

If cost is an issue then you could still drill them out and treat it, but then (ab)use some stainless rivnuts, but instead of setting them like you normally do to fixate them, just weld the 'collar' into the post. Or browse through a catalogue of stainless wire end fixings or similar and see which could be 'repurposed' for the same purpose.

Bye, Arno.

[Pants]

If those are stainless, I’ll eat that handrail. Probably some type of zinc or cadmium plated nut that when welded, burned off the plating.

I’d drill them out completely, plug the hole with a new piece of round stock that is pre-tapped for 6mm. You’ll chase your tail and never have the finish you seek trying to “fix” that crap.

I agree - not about the eating part - but looking at my own photos, I couldn't post the above until I'd actually tested them with a strong pickup magnet. And there wasn't even a HINT of attraction, so it's not just mild steel...

I like the plug-with-pretapped-slug idea. I'm totally green when it come to TIG, but I think I could manage to tack those plugs in with almost no filler and have it look decent.

edit: hey, wait a minute...if you're gonna eat them, you'd have to come here to do it, so how about I let you off of the 'eating' part and get you to do the re-fab instead?

[Pants]

as above, probably plated steel nuts, tho i wonder about exhaust grade stainless which is barely considered stainless.
i wonder why they fitted nuts, its cheaper and quicker to just tap it.
as above i would remove the nuts completely, plug and tap.

Exhaust grade sounds entirely plausible. I find it exhausting already.

But the tubing is thinwall (around 1/16") so it doesn't have sufficient strength to be tapped. Honestly, I'd rather they'd just left the CNC-drilled pilot holes for me. Stainless rivnuts would have been my fix for THAT...

[Pants]

Try sticking a magnet on the nuts. Likely they are highly magnetic and quite likely just plain (mild-)steel.

Could be 409 'stainless', which will definitely rust and is not suitable for these applications, but as it looks like it's even rusting inside the threads that seems unlikely.

Best option would be to drill these out completely, pickle the area to get any steel and rust contamination etched out, and then have some stainless threaded 'plugs' machined and then weld those in.

If cost is an issue then you could still drill them out and treat it, but then (ab)use some stainless rivnuts, but instead of setting them like you normally do to fixate them, just weld the 'collar' into the post. Or browse through a catalogue of stainless wire end fixings or similar and see which could be 'repurposed' for the same purpose.

Bye, Arno.

Yeah, we were thinking along the same lines, but there was not even the tiniest amount of magnetic attraction when I tested them.

What's the go-to pickle solution for this setting?

[cj737]

I like the plug-with-pretapped-slug idea. I'm totally green when it come to TIG, but I think I could manage to tack those plugs in with almost no filler and have it look decent.

edit: hey, wait a minute...if you're gonna eat them, you'd have to come here to do it, so how about I let you off of the 'eating' part and get you to do the re-fab instead?

Just let me know where and when, and I’ll throw a hood in the truck and come along. For reference, I’d use 304 round stock for the “plug” and I would recommend a bit of thin gauge filler wire. If you have some, 0.045 would be my choice.

[Arno]

Yeah, we were thinking along the same lines, but there was not even the tiniest amount of magnetic attraction when I tested them.

Weird.. Must mean that they are an alloyed steel, but not a normal chromium based like 304/316 (aka. A2/A4 on nuts), or the nuts have been heated to very high temperatures and the nickel and chromium have migrated/boiled from the upper layer so you're getting a more ferrous outer layer that rusts.

Contamination with some chlorine salts or having been exposed to (mild)steel fasteners can also transfer rust and start corrosion in the stainless steel.

What's the go-to pickle solution for this setting?

I have 2 small jars of a pickling and passivation gel from Weldline/Lincoln. One is called 'PICKLINOX' and the other is 'RESTORINOX'. Brush it on and let it sit for a while then wash it off with lots of water. Not sure if it's available where you live.

Very nasty stuff though (highly acidic.. Nitric and sulfuric acid.. Nothing to mess with..), so take extreme care when using and wear a respirator and face shield and full clothing cover.

Bye, Arno.

[Pants]

Yeah, we were thinking along the same lines, but there was not even the tiniest amount of magnetic attraction when I tested them.

Weird.. Must mean that they are an alloyed steel, but not a normal chromium based like 304/316 (aka. A2/A4 on nuts), or the nuts have been heated to very high temperatures and the nickel and chromium have migrated/boiled from the upper layer so you're getting a more ferrous outer layer that rusts.

Contamination with some chlorine salts or having been exposed to (mild)steel fasteners can also transfer rust and start corrosion in the stainless steel.

What's the go-to pickle solution for this setting?

I have 2 small jars of a pickling and passivation gel from Weldline/Lincoln. One is called 'PICKLINOX' and the other is 'RESTORINOX'. Brush it on and let it sit for a while then wash it off with lots of water. Not sure if it's available where you live.

Very nasty stuff though (highly acidic.. Nitric and sulfuric acid.. Nothing to mess with..), so take extreme care when using and wear a respirator and face shield and full clothing cover.

Bye, Arno.

Thanks, Arno. Belatedly. (I'm still not getting email alerts about responses to posts...)