Thread: Galvanising

There have been multiple reports of people galvanising them. Some have reported no warping, some have reported manageable warping and some have reported warping that is very difficult to deal with. It probably depends on how much residual stress there is in the particular bulkhead, but there would certainly seem to be some risk.

I would have thought the opposite would be the case, ie. that any stresses and strains in the steel would be 'ironed out' with the galvanising process.

Deano

Originally Posted by DeanoH

I would have thought the opposite would be the case, ie. that any stresses and strains in the steel would be 'ironed out' with the galvanising process.

Deano

That is exactly what happens. But consider how this "ironing out" is achieved. We have a piece of fabrication that is the right shape, but has built in strains due to the welding during fabrication. We now heat it up, which weakens the steel, and the strain is relieved - by stretching, bending, or shortening part of it. But the bit that changes shape or dimension is not going to be the bit that won't affect fitting it, except purely by luck!

What can be done is to male up a jig that can be bolted to the bulkhead, holding the bits that have to fit in the right place, so that the strain relief happens somewhere else. At a minimum, this would be a bar bolted to the two bottom mount points. This jig is galvanised along with the bulkhead. It goes without saying that it must be rigid and without incorporated strain itself.

Galvaniser I have used at least bases charges on weight of steel galvanised and a jig is likely to add considerably to this. Most likely jig would only be used once after getting galvanised in the process. So a consideration in its design could include subsequent use for something else. Most likely with some bits cut off and/or more added or the whole thing cut up for smaller bits of galvanised steel.

not to mention you have to make all the holes 1mm bigger..

can be fun...

Originally Posted by incisor

not to mention you have to make all the holes 1mm bigger..

can be fun...

...and 6 million more of them to let the gal flow in and out.

Mozzy

After restoring a S1 bulkhead I took a gamble and had it hot dip galvanised. I just delivered it to the galvos and picked up a week later, no jig or other engineering.
It didnt warp or distort. Maybe I was lucky? I do recall (this was 20 years ago) needing to ream out some bolt holes to clear out the slag.

C840 130716 4.jpgGalv Landy bits 210915 2.jpg

Here are pictures of the S3 bulkhead I had done, and had a S2 bulkhead done at the same time. My experience was the same as Grappler. The bulkhead didn't change shape, it bolted back in perfectly. The panels flexed a bit, the second photo shows that, it looks worse than it is, but they are not dead flat. The threaded holes all need to be cleaned out and re-tapped. One of the windscreen frames I had done did "warp" and needed to be straightened. I think that the warping was caused by it bumping into something else while it was hot, and it wouldn't need to be a terribly hard bump. It straightened out fine. I am not planning to paint the bulkhead (that's another story) but I don't think I would get one galvanised next time if it is going to be painted. Unless you are planning to drive through deep salty water a lot, decent prep and painting should give enough protection.