Rusted out inner wings <Picture heavy>

[Linegeist]

Yup, nice work Vanny! Especially given that 'orrible welder - they really ARE crap. Been there - ripped up the bloody Tee shirt in frustration too.

Burning off that galavanised coating won't have done much for arc stability either, introducing all sorts of weird gases into the shield mix. I've learned to either avoid it or grind it off first ... it makes for a much easier welding experience and enables you to concentrate on your wrist action!

Nice piece of work moosh. Top stuff!!!

[Vanny]

The fumes are not toxic but poisonous, subtle difference but one ends up dead and the other ends up ill.

From http://www.sperkoengineering.com/html/a ... anized.pdf

-------------
When zinc vapor mixes with the oxygen in the air, it reacts instantly to become zinc oxide. This is the same white powder that you see on some noses at the beach and the slopes. Zinc oxide is non-toxic and non carcinogenic. Extensive research(1) into the effects of zinc oxide fumes has been done, and although breathing those fumes will cause welders to think that they have the flu in a bad way, there are no long-term health effects.
--------------

(1) "Extensive Research" means Walsh, Sandstead, Prasad, Newberne and Fraker, Environmental Health Perspectives, Volume 102, Supplement 2, June 1994, 5-46. Provides summary plus 471 references.

So when well ventilated, under short exposure and drinking a glass of semi skimmed before hand, the risk is simple nausea and the likelyhood is low. Frankly when i have had to weld galv (usually rushing), i've never had any problems.

When the galve vapourises and produces zinc oxide, its simply adding another relatively inert gas, so i doubt thats going to gause much of a problem.

That said, getting the galv and galv oxide in the weld is going to make life LOT harder, usually crippling the arc, inducing defects and i suspect creating a whole world of pain as the galv and other crap slowly edges into the metals surface.

So yes, I do grind the surface back, more for quality than health.

Just so we are clear, this is far from the first time i've welded, but it is the thinest stuff i've welded. 90% of previous welding has been 2mm+ and probably 80% of that with stick, lovely stick, no pratting about with wire speed, just set the current and go. Thinking about it, nearly all my previous welding has been under supervision, so this time has been no exception!

[Linegeist]

Just for the record ..........

The zinc that is generally used for hot dipped galvanized coating has a naturally occurring lead content around 1/2%. Since
lead is not soluble in zinc over 0.9%, it cannot exceed 0.9% concentration. This lead may be vaporized along with zinc
during welding. Since lead does not vaporize until it gets over 3000°F, and since some of it is soluble in steel,
proportionately less lead is vaporized than zinc; lead oxide fumes, however, should not be inhaled,

When using SMAW ("stick") welding, galvanized steel can be welded in the same manner as uncoated steel. When using
MIG or flux cored welding, one may have to adjust the voltage slightly to control spatter, and one may have to clean the
welding gun of spatter and zinc oxide deposits more frequently that when welding uncoated steel. Hobart makes a flux cored
wire called “Galvacore” that some users have had good success with when welding galvanized steel.
When difficulty is encountered welding galvanized steel that was not encountered during welding uncoated steel, it is usually
because the Welding Engineer has not accounted for the volume of gas that is evolved by the vaporization of zinc during
welding. The thicker the zinc coating, the more fumes are generated, and those fumes have to be able to escape easily into
the atmosphere and not be forced through the liquid weld metal.
For example, welding galvanized plates to form a T-joint is a commonly troublesome situation. Since the galvanized edge
of one plate is butted against another galvanized surface, the zinc vapors that are formed at the abutting surfaces will not be
able to escape to atmosphere easily as the zinc is vaporized. Instead, they will blow into the weld pool, creating porosity or
a poor weld surface. This is aggravated when welding conventionally hot-dipped products, since the edges frequently have
excessively heavy zinc coatings. One solution is to separate the parts by 1/16 inch using wire spacers or fixtures which will
leave a gap for the zinc vapors to escape easily. Other approaches are to use a slight (15°) bevel on one member (Figure 1), to
remove the zinc from the faying surfaces by shearing or mechanically cuting the plate where the faying surfaces will meet, and
to abrasively remove most of the zinc from one or both of the faying surfaces (Figure 2). Any of these methods will
significantly reduce the amount of zinc between the parts, and this will reduce the volume of gas evolved, improving weld
quality.

http://www.sperkoengineering.com/html/a ... anized.pdf

[Vanny]

So how would i tell if a sheet had been hot dipped or sprayed?

[Linegeist]

So how would i tell if a sheet had been hot dipped or sprayed?

I asked a serious question, if you want to post tripe then please find somewhere else to do it!

My apologies for assuming a sense of humour..........

Sprayed Zinc has a texture lacking in dipped sheet does it not?

[Vanny]

I asked a serious question, if you want to post tripe then please find somewhere else to do it!

[mat_fenwick]

I've got to admit, that made no sense to me either!

Are you simply talking about molten zinc sprayed on to the surface versus immersion in a vat of molten zinc?

[Vanny]

I'm not talking about processes, i'm well versed with the process, but how you identify which is which i'm not so sure of, not without cutting out a sample, polishing the edge and looking at a macro level.

[mat_fenwick]

I think all the galv I've come across has been the hot dip type, where it appear the zinc crystals have grown to a size visible with the naked eye. I would think that sprayed on zinc would have smaller crystal sizes and probably a speckled appearance, but I don't know for certain.

[Vanny]

Made up a new towing eye this evening. Old (dead) one;




And the new, slightly thicker, slightly bigger one;



Much more in depth reading on the BXProject.

[KevR]

Brilliant work Vanny.

I am sure you are aware, welding galvanized sheet produces very toxic fumes.

If you are using 2mm thick sheet, then please grind off the zink surface from both sides of the welded edge back to the mild steel.

You will get a much better weld, and reduce the effects of inhaling the fumes.

Good luck

Agreed - nasty fumes from that stuff, and if you don't grind the galvanising off, AND you have a welder that's restricting you to the pigeon-poo end of the spectrum, then all you're doing is trying to weld to the galvanising coat, rather than getting decent weld penetration.

As far as the welder's concerned, you might find you can improve its performance a bit by:
1: making sure you're using the shortest possible extension leads etc, and of adequate wire size (no little orange leads intended for strimmers).
2: Turn off as many other current-consuming appliances as possible to keep the supply steady.
3: Get the best possible earth onto the car body - a bolted clamp's much better than the rubbish spring clamps usually supplied as standard.
4: A lot of cheap migs (my old SIP Migmate included) have very weakly-designed wire roller mechanisms so wire feed is hit and miss. I put an extra plate on the outside of the mech to stop the roller carriers flexing. Made a big difference - also keep the torch cable as straight as possible to keep the wire running through smoothly.

Every little helps!
Keep up the good work.