Mig welding galvanised sheet?

[John Morrison]

Hi all,

looking to do a few minor chassis upgrades, and the only stock sheet I've got that is 1.5mm is galvanised.

I've looked and heard every view from, Mig welding galvanised can't be done to the fumes will kill you to, scrape the surface and treat as normal.

Anyone give me the 'Heads Up' on the job.

John.

[ed_h]

The zinc will vaporize and make a good weld difficult.  The vapor is also mildly toxic.  Remove the zinc either by grinding it away from the weld area, or if the part is small enough, remove it all with acid.

Ed

[Bfg]

I'd agree with Ed, welding galvanised sheet just needs a quick removal of the plating   ..and that plating is of course only on the surface of otherwise common-or-garden mild steel.   I generally use the edge of a linishing disc on my angle grinder or drill,  or else a power file to locally remove it just along the weld line.   If not cleaned off (perhaps just scratched through with a screwdriver or old chisel) then the zinc makes a lot of white smoke so visibility is lessened ..but still workable  ..and you're likely to get more rolling splatter.  The galvanised on the back of sheet will blister and burn off too.

I tend not to weld within the confines of my airing cupboard and the ventilation in my garage is generally fine ..so to the best of my knowledge  - I've not yet died nor turned green as a result,  but my mental state when talking about Triumph cars or Sunbeam motorcycles is frequently called into question.

Pete.

 

p.s.

1 hour ago, ed_h said:

remove it all with acid.

I've not tried that Ed, what acid do you generally use ?

Thanks.

Edited May 4, 2020 by Bfg

[ed_h]

Muriatic works well and is easy to get.  You can dilute it 2 or 3 to 1 and it still works pretty well.  Best to do it outdoors due to the smell and the fumes can be corrosive.

Ed

Edit:  acid works best if you  can immerse the part.  Wiping or brushing it on would take too long.

Edited May 5, 2020 by ed_h

[Waldi]

Hi John,

One other aspect. The sheets with Zn on it are often a harder grade, making it more difficult to bend. I bought a large sheet of 1 mm “body plate” which is relatively soft, and had the coating on it which allows welding and easy marking.

Abd maybe not vital, but 1 mm weights less and is easier to cut.

Cheers,

Waldi

[Ian Vincent]

At the risk of being technical ....

when steel is galvanised you get two steel/Zn alloy layers between the steel and the zinc. Those alloy laters are harder than the base steel which is what makes it harder to bend. 

Grinding off the zinc is still likely to leave the alloy layers which is a good thing as they will still provide corrosion protection but you will get some fumes. The old pro’s trick was to drink a glass of milk before starting to weld. 

Rgds Ian

PS sulphuric acid (e.g. battery acid) is best for removing galvanising. It’s what is used industrially. 

Edited May 5, 2020 by Ian Vincent

[RogerH]

One of the medical symptoms of inhaling the zinc fumes is Flu like symptoms. head ache, wet/runny nose etc.

So try not to breath it in.

Roger

[john.r.davies]

Not wishing to be contraversial in any way ... but, what about "Zinc-rich Weld-through Primer"?

[stuart]

4 minutes ago, john.r.davies said:

Not wishing to be contraversial in any way ... but, what about "Zinc-rich Weld-through Primer"?

What about it? You only use a very thin coat of it and its nowhere near as "Rich" as the name implies, you could use the Copper version if you prefer. With any welding/soldering/brazing you should always have good ventilation.

Stuart.

Edited May 5, 2020 by stuart

[stillp]

2 hours ago, Waldi said:

 

Abd maybe not vital, but 1 mm weights less and is easier to cut.

 

1mm for the chassis? 

Pete

[john.r.davies]

6 minutes ago, stuart said:

What about it? You only use a very thin coat of it and its nowhere near ad "Rich" as the name implies, you could use the Copper version if you prefer. With any welding/soldering/brazing you should always have good ventilation.

Stuart.

Really?    Zinc primer can contain as much as 85% of metallic zinc (https://www.steelconstruction.info/Paint_coatings#Zinc_epoxy_primers), and a coat of paint will probably be thicker than the 85 microns of typical galvanizing.

"Metal Fume Fever" is a real thing, as are the many diseases caused by metal poisoning in metal workers, before H&S.     Take them seriously, but not too seriously, unless you intend to weld a tank together.

[RogerH]

Hi John,

There isn't much paint in a aerosol can. Most of it is thinners and propellant.

the metallic part is 85% of not a lot.

For weld through use,  you are attacking verty small areas so the total coming your way is not a lot on any scale.

But, yes do take care.

 

Roger

[ChrisR-4A]

12 hours ago, John Morrison said:

Hi all,

looking to do a few minor chassis upgrades, and the only stock sheet I've got that is 1.5mm is galvanised.

I've looked and heard every view from, Mig welding galvanised can't be done to the fumes will kill you to, scrape the surface and treat as normal.

Anyone give me the 'Heads Up' on the job.

John.

Hi John, we've all been there, we go to do a job and this piece of "not ideal for the purpose material" is shouting at you "Use Me, Use Me" from a distant corner of the garage. Hard to resist but invariably you use it anyway and it takes twice as long and is never quite as good as what you really needed. 

Metal can still be bought on line delivered to your door, I have used "Metals4U. Co. Uk they do most materials from 1m lengths upwards. Other companies are available. 

I would bite the bullet  and get the correct steel for the job. 

Chris 

[Bfg]

43 minutes ago, ChrisR-4A said:

get the correct steel for the job. 

Might I ask - what is the correct grade and thickness of steel for Triumph chassis repair,  for chassis 'upgrades',  and also for body tub repair.  

This is a serious still-a-newbie question ..because I'll be into that sometimes soon. 

Thanks, Pete.

[stuart]

33 minutes ago, Bfg said:

Might I ask - what is the correct grade and thickness of steel for Triumph chassis repair,  for chassis 'upgrades',  and also for body tub repair.  

This is a serious still-a-newbie question ..because I'll be into that sometimes soon. 

Thanks, Pete.

I use 3mm plate for re-enforcements on the diff bridges 2mm for chassis sectional repairs and 1.2mm for panel work.

Stuart.

[John Morrison]

Hi all,

as expected lots of help and experience, so thanks.

I think Chris is correct, and I will track down some 1.5mm mild steel sheet and do the job properly,

It's not like I need the TR this weekend!

That said having 'Found' the galvanised,  I will have a mess around with various settings etc., I will let you all know any real differences in using, for future reference.

John.

 

[stuart]

Just now, John Morrison said:

Hi all,

as expected lots of help and experience, so thanks.

I think Chris is correct, and I will track down some 1.5mm mild steel sheet and do the job properly,

It's not like I need the TR this weekend!

That said having 'Found' the galvanised,  I will have a mess around with various settings etc., I will let you all know any real differences in using, for future reference.

Pete, chassis 1.5mm, body 0.9mm.

John.

 

Too thin see above.

Stuart.

[John Morrison]

Hi Stuart,

yes I saw that and edited mine, you posted while I was typing,

course going with your thoughts.

John

[Bfg]

1 hour ago, stuart said:

I use 3mm plate for re-enforcements on the diff bridges 2mm for chassis sectional repairs and 1.2mm for panel work.

Stuart.

Thanks Stuart.

Might I assume the original was perhaps ; 12 swg (2.64mm) for chassis brackets like suspension mounts,  14 swg (2mm) for other brackets - like those for body mountings,  16 swg (1.6mm) for the chassis rails, and 18 swg (1.22mm) for the body tub and panels ?  

 

As a bit of an off-thread,  assuming John doesn't mind a very quick diversion..  does anyone happen to know the exact size of the main chassis rails, so that I might have straight lengths folded up ?   ie., outside and inner section, sorta like   [‾‾ [‾   which would be an interference fit to be spot-welded along their edges to form the familiar flanged box section ?

Thanks,  Pete.

[Charlie D]

6 hours ago, john.r.davies said:

"Metal Fume Fever" is a real thing

I thought I’d look it up on the Internet to see what I could discover.
A couple of things:
 
“…Metal fume fever, is also known as brass founders' ague, brass shakes, zinc shakes, galvie flu, metal dust fever, Welding Shivers, or Monday morning fever…” 

(Not the same as ‘Saturday night fever’, I assume)

 

“…The MFF is characterized by fever, cough, sputing, wheezing, chest tightness, fatique, chills, myalgias,  dyspnea, leukocytosis with a left shift, thirst, metallic taste, and salivations…”

Doesn’t sound very pleasant does it, but if ever you want to impress someone down the pub you could learn those two sentences off by heart and just drop them into the conversation every so often.

Charlie.

[Waldi]

7 hours ago, stillp said:

1mm for the chassis? 

Pete

Hi Pete,

Sorry for the confusion, no 1 mm would not be ok for chassis work, think I used 2 mm for that, anyway the same as  the original thickness.

Cheers,

Waldi

[john.r.davies]

1 hour ago, Charlie D said:

I thought I’d look it up on the Internet to see what I could discover.
A couple of things:
 
“…Metal fume fever, is also known as brass founders' ague, brass shakes, zinc shakes, galvie flu, metal dust fever, Welding Shivers, or Monday morning fever…” 

(Not the same as ‘Saturday night fever’, I assume)

 

“…The MFF is characterized by fever, cough, sputing, wheezing, chest tightness, fatique, chills, myalgias,  dyspnea, leukocytosis with a left shift, thirst, metallic taste, and salivations…”

Doesn’t sound very pleasant does it, but if ever you want to impress someone down the pub you could learn those two sentences off by heart and just drop them into the conversation every so often.

Charlie.

We speak of little else down at the Engine Fettler's Arms!