Working with/welding galvanised steel

[ELL]

Is it possible to weld galvanised steel? If not how are welded galvanised panels made? Are they welded first then galvanised?

I'm going to make my own trailer ramp using box section and mesh and I want it all galvanised. If I buy the mesh and box section already galvanised will I problems trying to weld it? Thanks.

 

[colnerov]

Traditionally it's welded then galvanised, however you can weld it afterwards, but you need to remove the Zinc/galvanising first to get a decent weld. Then paint with Galvafroid. Don't forget the fumes can give you 'Galv flu', not pleasant. The other thing if you're doing it in box section, either leave the ends open or drill vent holes, 10mm minimum.

 

[dieselsamurai]

I use a cutting wheel on edge to grind off the galv you can see the colour change when your through it , flap wheels or grinding flat on tends to smear it

 

[ELL]

Traditionally it's welded then galvanised, however you can weld it afterwards, but you need to remove the Zinc/galvanising first to get a decent weld. Then paint with Galvafroid. Don't forget the fumes can give you 'Galv flu', not pleasant. The other thing if you're doing it in box section, either leave the ends open or drill vent holes, 10mm minimum.

What are the vent holes for? Thanks.
Also, can you recommend a certain brand of galvafroid? Cheers.

 

[rtcosic]

What are the vent holes for? Thanks.
Also, can you recommend a certain brand of galvafroid? Cheers.

When the item is dipped in the molten zinc air trapped inside will expand rapidly. This can distort the item. Vent holes allow this to escape.

Venting and drainage of steel

Where hollow sections are sealed they must be vented for reasons of safety so allowing the escape of air and the ingress and drainage of zinc during the dipping process. Vent holes are required at each sealed end either in the end plate or the section. Where holes are provided in end plates they...

galvanizing.org.uk

Galvafroid is the brand name.

 

[Stupoty]

Traditionally it's welded then galvanised, however you can weld it afterwards, but you need to remove the Zinc/galvanising first to get a decent weld. Then paint with Galvafroid. Don't forget the fumes can give you 'Galv flu', not pleasant. The other thing if you're doing it in box section, either leave the ends open or drill vent holes, 10mm minimum.

Vent holes is something people easily forget , the galvanisers probably have a data sheet with details of the holes they want.

Cost a fair bit per hole the galvanisers drilled last time someone forgot them

Stu

 

[bigegg]

What are the vent holes for? Thanks.
Also, can you recommend a certain brand of galvafroid? Cheers.

Vent holes are also useful to allow any water which gets inside to get out, rather than rusting out the box sections.
I like to pour a glug of engine oil inside before the final weld and swish it about afterwards.
Gives a good coating to the inside where you've burnt off the galv.

NOT if you're sending it to be galvanised afterwards!

For galvafroud, I use "prosolv" from 'bapps for bolts" (not sure if they're nationwide) - about £6 for an aerosol.

 

[500e]

The tube / box can also explode if sealed causing molten Zinc to fly about.
Do not let them drill the holes = cost, and holes could be anywhere

 

[Islander71]

"Zinga" is also very good for touching up where the galvanising has been removed.

 

[Munkul]

You can mig braze zintec... works really nicely. not sure about proper galv though.

 

[chrismac]

Vent holes is something people easily forget , the galvanisers probably have a data sheet with details of the holes they want.

Cost a fair bit per hole the galvanisers drilled last time someone forgot them

Stu

At least they drill them where you are, the stuff I saw years ago, it looked like they blew holes in it with a burning torch!

 

[Ed.]

Usually galvanizers will put the metal into vats of acid to clean the steel before dunking them into vats of molten zinc. The holes have to be positioned into places where the acid can run out freely so that when the metal is swapped into the molten zinc an explosion doesn't result. If the metal is a sealed RHS/SHS beam or pipe with no escape holes, the pressure will build up and sometimes a weak seam or poor weld results in an explosion of molten zinc spraying everywhere which is very dangerous for everyone working there.

One of my friends I used to hang out with when I was much younger, used to live opposite a galvanizer and occasionally you would hear a loud explosion, nowadays I doubt that you will find any company that will take tube type steel that hasn't enough openings in it

 

[Erie Fred]

I have heard they keep a torch handy at the galvanizers, and blow a hole in where ever they want to if you don't.

 

[Munkul]

Ours keep a raft of battery drills handy for drilling holes wherever they like, at £3 a pop.

 

[chrismac]

Usually galvanizers will put the metal into vats of acid to clean the steel before dunking them into vats of molten zinc. The holes have to be positioned into places where the acid can run out freely so that when the metal is swapped into the molten zinc an explosion doesn't result. If the metal is a sealed RHS/SHS beam or pipe with no escape holes, the pressure will build up and sometimes a weak seam or poor weld results in an explosion of molten zinc spraying everywhere which is very dangerous for everyone working there.

One of my friends I used to hang out with when I was much younger, used to live opposite a galvanizer and occasionally you would hear a loud explosion, nowadays I doubt that you will find any company that will take tube type steel that hasn't enough openings in it

And even the orientation they choose to dip it, ie if its a folded up section, we might think okay that will get dipped one way but the galvanisers need to dip another way, I have seen holes blown in replacement trailer sides due to this issue where the folded sides would create a basin of acid/zinc.

 

[Stupoty]

Ours keep a raft of battery drills handy for drilling holes wherever they like, at £3 a pop.

They sound nice and helpful. I wont tell you how much the place we use charges but it's a bit more than that

Stu

 

[KemppiFrog]

My outfit in La Rochelle has pictures of what happens and a big warning of what it costs you if you don't drill enough. There is also a bunch of pix overwritten to show how..
I buy a lot of pre hot dipped galve tube for things like garden pergolas. Use an angle grinder the shamfer the the edges to be welded. What does tend to happen, is a bit of the zinc gets in the weld and they are less likely to rust. I have tested to distruction welds with no preparation and found them strong enough. Obviously not breathing the fumes....