Protecting threaded rod

[Dr.Al]

For an upcoming project, I'm going to need to weld some threaded rod in place (it'll be welded in a few places along the length). As I don't like the idea of Welding Shivers, I plan to dunk the (BZP) threaded rod in citric acid for a while before welding it. That will, of course, remove the zinc and hence remove the corrosion resistance. What are the best options for re-adding some semblance of corrosion resistance, bearing in mind it'll be a relatively long length of threaded rod and that I want the thread to still be usable (so I can't just cover it in paint!)?

 

[tom2207]

ACF 50 ,,, spray tin ,, its great.

There are a fair few zinc rich paints and the likes , Galvafroid springs to mind , but the trouble is that if you want to run nuts up and down the thread etc it can just get horrid and sticky , then wears off , depends on what you want to do at the end of the job , obviously only clean the bits your welding a rub with a waterproof grease may work too , I just Like ACF 50 , but it needs a squirt every couple of years , hence the spray tin idea although even it can get a tad tacky.

 

[mike os]

Might as well buy plain rod then saves taking the plating off but if it’s only a few welds do it in a ventilated place

 

[EM1L4]

Would a stainless rod be an option?

 

[Dr.Al]

Would a stainless rod be an option?

Interesting thought, but I'm trying to do this on the cheap! There's quite a lot of threaded rod in total over all the pieces and I've got loads of BZP stuff already.

 

[Paul.]

If you are stick welding or migging it then just do it in a ventilated area, tig might be more troublesome coping with the plating, but the thickness of coating on BZP studding is not going to be enough for a few tacks to cause you problems, put a mask on if you are worried,

 

[dan.taylor.1]

You can buy plain steel threaded rod, or as Paul said, just weld it. Its bzp not galvanised, there's so little zinc there as long as you do it in a well ventilated area (put a fan on maybe, or by the door with a breeze) you'll be fine. As above, stick a mask on if you're worried. Also recommend the cold galv spray paint, a few tips, they're not all made equal, the more expensive ones are usually so because there's more zinc in them, and DO shake them VERY well before using to mix the heavy zinc up in the paint.

 

[Dr.Al]

If you are stick welding or migging it then just do it in a ventilated area, tig might be more troublesome coping with the plating, but the thickness of coating on BZP studding is not going to be enough for a few tacks to cause you problems, put a mask on if you are worried,

It'll have to be TIG as I don't have a MIG welder and my stick skills are close to non-existent!

 

[dan.taylor.1]

Ah I'd grind it off for tig for sure. Saves messing the tungsten up and filling the cup with white plumes. Still, I'd just do it in plain threaded rod and paint after.

 

[Dr.Al]

Ah I'd grind it off for tig for sure. Saves messing the tungsten up and filling the cup with white plumes. Still, I'd just do it in plain threaded rod and paint after.

You never know, maybe I'll be brave and give stick welding another shot

 

[zx9]

You never know, maybe I'll be brave and give stick welding another shot

Have a practice on some mock up parts.
FWIW I was amazed by how easily my Tig inverter burned rods the first time I tried it much easier to strike than the buz box of old.

 

[AndersK]

Just put them in the bath standing and remove only about 20 mm of coating.

 

[Dr.Al]

Have a practice on some mock up parts.
FWIW I was amazed by how easily my Tig inverter burned rods the first time I tried it much easier to strike than the buz box of old.

Don't worry - I'll definitely be practising before doing anything for real. The part that the (M12) threaded rod will be welded to is 25 × 25 × 2 mm box section so I'm very nervous about trying to stick weld to that given how thin it is. I've only tried stick welding to 6 mm steel before. I think I've got some thin rods (1.6 mm 6013s), although I've only got 6 or so of them so would need to buy more if they're going to be the way I do it. I've also got lots of 2.5 mm ones so I'll try them too.

At least with stick welding I can do it all outside and not have to worry so much about fumes etc. Would it also save me from having to get the mill-scale off the box section as I have to when TIG welding?

 

[zx9]

Don't worry - I'll definitely be practising before doing anything for real. The part that the (M12) threaded rod will be welded to is 25 × 25 × 2 mm box section so I'm very nervous about trying to stick weld to that given how thin it is. I've only tried stick welding to 6 mm steel before. I think I've got some thin rods (1.6 mm 6013s), although I've only got 6 or so of them so would need to buy more if they're going to be the way I do it. I've also got lots of 2.5 mm ones so I'll try them too.

At least with stick welding I can do it all outside and not have to worry so much about fumes etc. Would it also save me from having to get the mill-scale off the box section as I have to when TIG welding?

Go with the 2.5mm and keep it toward the threaded rod and you will be fine.

 

[Dr.Al]

Go with the 2.5mm and keep it toward the threaded rod and you will be fine.

Yeah... I still think stick welding is hard! TIG always feels fairly natural (and being slower, is much more controllable). This feels like pot luck!

It does at least appear to have stuck (this was several attempts in after tweaking the current a lot). These were all done at the same current (with very different results) and on 20 × 20 × 2 mm box instead of the 25 mm stuff as that's what I had an offcut of. At least it doesn't appear to have gone more than half-way round the thread though (it's important that the outer half of the threaded rod is still formed correctly). I'll do some more practice welds once I've cut a few more bits of box up to play with.

It's all gone a bit pale grey - is that an indication that the zinc-plating is no longer protecting it? If so, there's not much benefit to doing this over cleaning it all off and getting the TIG fired up (although I won't have quite such a high density of welds in the final thing, so it might not be quite so bad in practice).

I might also try citric acid-ing some threaded rod and then try TIGging it to some clean box for comparison. If I go that way I'll have to get hold of some drain pipe or similar as some of the threaded rod lengths will be 1.8 m long...

 

[jimbo84]

The best tip for stick welding I ever got (from this forum too) was to shove the rod in a lot further than you think it should be, it's always worked a treat for me since. I'm in no way experienced enough to comment but I think it would have helped with those welds, particularly the middle weld of the big ones.

 

[dan.taylor.1]

Use enough amps so when you hold a tight arc it doesn't stick, then keep a tight arc.

 

[Arc Tourist]

For an upcoming project, I'm going to need to weld some threaded rod in place (it'll be welded in a few places along the length). As I don't like the idea of Welding Shivers, I plan to dunk the (BZP) threaded rod in citric acid for a while before welding it. That will, of course, remove the zinc and hence remove the corrosion resistance. What are the best options for re-adding some semblance of corrosion resistance, bearing in mind it'll be a relatively long length of threaded rod and that I want the thread to still be usable (so I can't just cover it in paint!)?

Unfortunately, I remember a project we did for the city sewer plant. We were actually surprised when horridly rusted old cover plates easily came off because the bolts were previously coated with anti-seeze compound. Perhaps this is an economical solution for your purpose.

 

[Dr.Al]

I've had lots to do for the last few evenings, so didn't get much workshop time. However, I went out this afternoon and found that the test piece of zinc-plated threaded rod that I'd (badly) stick welded to some box section is now rather rusty:

The heat from the stick welding has presumably vaporised the zinc (it looked very dull grey after welding) and the protection is long gone. Given that the zinc doesn't stay put and that I am so inept at stick welding, I think I'll go back to plan A: citric off the zinc plating and TIG weld the rod to the box section, something like this:

That was my first attempt and looks quite a bit better to me than my fourth attempt at arc welding! TIG is also a much more enjoyable process than stick.

I've got some ACF50 now, so I'll spray some on the test piece and see what it looks like when it's dried/cured/whatever it does.

 

[AndersK]

Now I'm confused, whats that gonna become???