Surprise surprise, it's galvanized

[TR6oldtimer]

Started preparing the driver's side floor pan and much to my surprise the sheet metal is lightly galvanized. Not just that thin barely visible coating of gray you expect, but real zinc metal. How do I know? Well there is that lovely white zinc oxide residue all around my welds. The fumes from this stuff are not good for you.

While the galvanized pans should hold up better then the originals (like at my age I should care), I now have to deal with better ventilation when welding and the metal prep for galvanized sheet metal.

 

[tdskip]

While the galvanized pans should hold up better then the originals (like at my age I should care), I now have to deal with better ventilation when welding and the metal prep for galvanized sheet metal.

Hey - doing it right is its own reward some time.

Nice to find that parts quality is actually OK on the floorboards. Who did you source them from?

I've heard those fumes are nasty - be careful!

Any updated picture for us?

 

[angelfj1]

Don't take it too lightly, you only get one pair of lungs

But, there are other considerations regarding the integrity of the weld

The requirements to weld galvanized steel raises three questions.

What procedures must be modified or employed to maintain the integrity and quality of the weld?
What precautions should be taken to protect the welder from zinc fumes?
How should the weld be repaired to maintain the integrity of the galvanized coating?

1. Weld Procedures


If molten zinc gets into the molten weld metal, it can cause inferior welds and weld cracking. For structural quality welds the zinc should be removed in the immediate area of the weld and within 15 mm of either side of the weld. This can be done by:


i) grinding the zinc off.

ii) chipping heavier zinc coatings off with a chipping hammer or a chisel.

iii) burning the zinc off with an oxy‑acetylene torch; such as would occur during bevelling to prepare the material. (Adequate ventilation should be provided ‑ see Zinc Fume.)

For non-critical welds when hotter burning welding rods are used, the heat of the welding process can vaporize the zinc before it can run into the weld metal. The following procedures are recommended to reduce the availability of molten zinc near the weld.

i) Prepare the bevels to eliminate the formation of a reservoir of molten zinc between the fraying surfaces at the root of the weld metal.

ii) Slightly increase the size of the gap at the root of the weld.

iii) Use a whipping motion to burn the zinc off ahead of the weld.

iv) Use a slightly slower travel speed.

The publication "Welding Zinc‑Coated Steel" published by the American Welding Society, Inc. provides excellent detailed information on the recommended procedures to weld galvanized steel. The American Hot Dip Galvanizers Association reprints from the Welding Journals provide additional information.

2. Zinc Fume

While zinc fume is non‑toxic, excessive dosages can result in zinc fume fever ‑ an extremely unpleasant reaction with symptoms that resemble a serious fever. However, recovery is generally rapid and there appears to be no long‑term affects from zinc fumes. Mechanical or natural ventilation or an approved respirator and eye protection should be utilized when welding galvanized steel. Of course, removing the zinc before welding will significantly reduce this concern. Drinking milk can both reduce the risk of getting zinc fume fever, and also reduce the fever if you have it.

The following respiratory equipment will provide the necessary protection when welding and/or cutting galvanized steel.



Respirator: #1 North 77BP Low profile type, fits under a welding helmet

#2 North 7700 Half mask type, for use with cutting goggles

#3 North 7190 Disposable, low profile type, fits under a welding helmet

Cartridges: Use with #1 and #2 above #1 North 7500-8 Dusts, fumes, mists and radionuclides (zinc fumes)

#2 North 7500-81 Organic vapors, dusts, fumes, mists, radionuclides, radon daughters; paint, laquer and enamel mists; and pesticides

(Dual protection when zinc and paint fumes are present)



3. Repair

Repair procedures are well specified in ASTM A780. In addition, our "Specification for Hot Dip Galvanizing", "Repair Procedures #27" in our in‑house training program, and "Field Repair Procedure" in this brochure, specifically detail how to repair damaged galvanized steel. It should be noted that in addition to the repair, the zinc adjacent to the damaged area will provide cathodic protection which unlike paint films, will prevent underfilm corrosion of the adjacent material and will significantly retard corrosion of the bare areas.

 

[Don Elliott]

My floors and all the inner sills and rockers were full of rusty holes when I did my restoration from 1987 to 1990. I put in standard repro parts just like the originals. Quarter panels too. I had each part of my TR3A sprayed off the car. After 97,000 miles it still looks like new. Nothing had been galvanised. Think about it, I would guess that I drove about 3,000 miles during these last 17 summers in the rain. When the under mats got soaked, I removed the seats and took out the carpets and mats to let them dry. There is no rust anywhere on the car. The floor panels under the carpets look like they were sprayed yesterday. And all the bottom was finished and painted like the top side. There is no tar or dum-dum in the joints. There is no sealer or undercoating under the fenders or under the car. Up under the fenders looks shiny - like new.

Think again about the need for galvanizing with all the disadvantages. My car will last another 100 years the way it is.

It's lasted me 50 years up to now. This coming Thursday will be its 50th birtday since it was "born" in Coventry on St. Valentine's Day in 1958.

Don Elliott, Original Owner, 1958 TR3A

 

[TR6oldtimer]

Thanks for the tips on welding galvanized metal. I did in my youth weld heavily galvanized steel. Thought then it was neat having all the white smoke poring out of the garage, but boy, did I have a heck of a night later. Drank a lot of milk and rested. My Father had little sympathy, only asking what I learned.

By the way, the coating on the floor is not like hot dipped or heavily galvanized steel, but enough that you see the oxide.

TD, I purchased the pans from TRF. The passenger side was not like this, and was only 22 gauge. This pan is 20 gauge. I do not know why there is a difference, but there is. Oh, the bit about old age was just me feeling my aching bones. I'll post pictures as I proceed with the replacement, hopefully remembering what I learned on the passenger side will make this side easier.

 

[Guest]

Strange, both the Heritage floor pans I got from TRF were black-painted (shipping paint) 22 gauge steel. No coating.

 

[Geo Hahn]

...When the under mats got soaked, I removed the seats and took out the carpets and mats to let them dry...

A PITA but that single step is enough to make the stock floorboards last a looooonnng time.

 

[Don Elliott]

Nice fence George. I do the same. When I was driving back from VTR in Portland Oregon in 2000 (7225 miles that trip),
I had the top down in sunny weather for the whole three weeks, that is, until the last day. I was in North Bay, Ontario, about 300 from home when the skies fell all over me. I got soaked, but I was determined not to put the top up. When I got home, my interior carpets and underlay were soaked. It took about 3 days for it to get dry.

Imagine if someone gets it all that wet, and lets it sit there. Now you can see why floor pans used to rot.