13 replies to this topic

[blue blood]

Hey everybody i just wanted peoples opinions on galvanising a front subframe. I have seen on the 16v mini forum a subframe before that has been galvanised do you think it will work properly on a standard subframe without warping to much? I would go for powder coating but its just a bit naf you knock it and it chips of and if moisture gets under it it flecks of at a very fast rate i just want a more substantial anti rust hard wearing finish! Regards Blue

[orcadian]

I had the front (auto, because I had a new one!) frame on my MPI Clubman Estate hot Zinc sprayed many years ago by Mersey Metal finishers in Bootle, Liverpool (don't know if they are still going but yellow pages might turn a company up in your area) They first took the brand new frame and shot blasted it all over and then immediately gave it the treatment with hot zinc - not galvanising. I then put 2 coats of silver hammerite over that and there is not sign af any rust. I didn't weigh it before and after, but I don't think the difference was great.

[tommy13]

I'm not an expert on zinc coatings, either hot dipped or electroplated. I think I read somewhere that electroplating can make the steel brittle and the hot dip can have problems with distortion.
My main point is that after 25 years of testing, I don't ever remember failing a Mini for a rotten front subframe. A couple of coats of paint and a waxoil will do, but I'm not too fussy on appearence. If you can get it hot dipped it should never need attention again.

[pikey7]

galvanizing will warp it. It was never designed to be hot dipped, so hasn't been relieved accordingly.

Best way I've read about having it done is to have it completely stripped, zinc rich primer sprayed (or possibly dipped), then epoxy and urethane coated.

Or the cheap (and old fashioned) way... strip, zinc primer, coach paint, waxoyl in the joints.

[Cooperman]

I've never bothered with the front sub-frame as they don't really rust. I did have a rear one sand blasted and hot-dip galvanised many years ago and it was superb after I then painted it with red-oxide primer and gloss black chassis paint. However, it was not cheap and as my car have been mostly rally cars the expense was not justified. I just re-paint the new frame with black chassis paint, then Waxoyl the frame, together with the rest of the car, every year.

[1984mini25]

Or the cheap (and old fashioned) way...

Clean it, hammerite and then let the good old a-series pee oil all over it.

[Wright&Wright]

Or the cheap (and old fashioned) way...

Clean it, hammerite and then let the good old a-series pee oil all over it.

Pretty much how mine's survived 23 years unscathed.

[MRA]

I'm not an expert on zinc coatings, either hot dipped or electroplated. I think I read somewhere that electroplating can make the steel brittle and the hot dip can have problems with distortion.
My main point is that after 25 years of testing, I don't ever remember failing a Mini for a rotten front subframe. A couple of coats of paint and a waxoil will do, but I'm not too fussy on appearence. If you can get it hot dipped it should never need attention again.

Yes electroplating can make steel brittle.... it is commonly known as Hydrogen Embrittlement, and is caused by the action of Zinc on Carbon, ie high tensile steels..... this is why you will never see high tensile bolts that have been elctroplated, well not "proper" high tensile bolts any way.

Any part that is affected can fail at any time, if you plated a high carbon (high tensile steel) it may last for 5 minutes or it may last for 1000 hrs, there is no way of knowing which unless you xray it regularly

Affected parts snap just like a carrot, I have seen bolts fail after being torqued up, whilst others within the batch still haven't failed after 5 years of service (it was a foreign machine tool), however this just goes to show how random the material is that is used for some of these bolts / parts..

However, galvanising a mild steel frame which has been welded using low carbon (mild steel) filler metals (rod or wire) will not be affected by this process. I have been told that the cleaning process can also have detrimental effects on the steel, although I habve not seen any evidence of this yet.

[bobs]

galvanizing will warp it. It was never designed to be hot dipped, so hasn't been relieved accordingly.

Agreed, if some numptie just chucks it in...

But they don't warp if the frame is prepared/seam welded up and the hot dip process done properly, I've got living proof!

I still think the 20+ year life span is worth the cost of getting a rear one done properly.

As for fronts, just strip and paint it well, they rarely go, there are loads of second hand front subbys about to prove this.

[kurt1991minicooper]

http://www.competiti...om/?page_id=299

These guys offer a service so yes its definitely possible
I will be galvanising both frames in near future so will let you know results

[tiger99]

It should be ok. I see that the possibility of seam welding it first has been raised by bobs, and that is a good idea anyway. I would do that whether galvanising or painting, as with MIG it does not take all that long or cost very much, and the added rigidity will do no harm whatsoever to the life of the frame, or the handling, or even the appearance.

Same for the rear, and I see that a lot of pattern subframes really need to be properly welded. The Chinese or whoever makes them tend to skimp on the number of spot welds, below the safe minimum calculated by BL originally. It is easy to seam or partially seam the vital bits.

mra-minis.co.uk also makes a very important point. Avoid all electroplated bolts, except for trivial things, where you may want them to be chromed. Hot rodders, especially in the US, often chrome plate everything in sight, and I often wonder how many are killed as a result of brittle fracture in something important. I have even seen coil springs plated, which is a complete no-no. And it is not just zinc, any form of electroplating causes hydrogen embrittlement. However, the aircraft and various other industries do use plated bolts, which are baked immediately after plating, in a tightly controlled process, to remove the hydrogen. Apparently, all companies which plate aircraft parts know how to do it properly, and their services should be used when plating vital bits of your car.

There are mechanical and hot dip processes for zinc and other metals, which do not cause embrittlement, but it is important to know what has actually been used on your vital bits, and whether it was applied correctly.

But the plating problem is not clear cut, and if in the slightest doubt, avoid. You don't need plated bolts on your big ends! Nor do you need stainless, but that is another can of worms, as I fear that some people building Minis right now will only learn the hard way.

[tiger99]

You can build a frame, probably out of box section, and it may well be very useful as a subframe jig for future projects, for instance location all the suspension mounts correctly if you cut up a frame to fit a foreign engine.

But I am not convinced that an experienced galvanising company will not be able to dip the frame without warping it.

[kurt1991minicooper]

A bloke who works for my dad advised me that galvanising both frames would be ok and no they would not warp. The way the steel has been formed gives it plenty of extra strength anyway. So im just drilling aload of 10mm holes in the rear subframe and front which also has been strengthened mondo sport style.

[kurt1991minicooper]

any pics? did you just bolt it to the subframe and what about were the subframe connects to the jig would you not have untreated areas?