original subframe advice

[mricsman]

I've got a one-owner car with its original rear subframe. Whilst the frame is structurally sound there is slight surface rust in the usual places, on the horizontal flanges etc, where the paint is detached. I'm keen to retain as much originality on the car as possible and would welcome some further advice. Should I:

1. Remove the subframe complete, have it shot blasted and re-painted, or

2. Remove the areas of loose paint only and treat the bare metal insitu?

Opinions please...

Many thanks.

[andy1071]

I would suggest removing it and getting it blasted, then a good rust killer, and painting. -Do it once and do it proper -as my dad used to say...

-I suppose the very best thing, if you really want to do it properly, is to get it chemically dipped, and then etch-primed or galvanised. Maybe that's a bit over the top (it would stop any future problems though!)

[mk1]

If true ORIGINALITY Is what you are after then scrub the loose flaky rust & paint off using a wire brush or similar, this is probably easiest done off the car, then paint the raw areas & give the whole thing a really good thick coat of any of the waxoyl type products that are available.

My personal preference would be to blast & powder coat with satin black, I would still also treat the internal nicky nocky corners with wayoyl type stuff too though.

[YMJ]

acid dipping is only worth it if you select the black electrothingy treament offered by them (SPL) after the actual dipping.

I KNOW THIS TO BE TRUE TO MY COST!

it is the ONLY way of totally neutralising the acid left in those nicky nocky (sic) corners and holes. Etch priming afterwards is NOT sufficient. I now have to spend my remaining lifetime squirting WD40 all around my car to prevent the rust spreading across the paintwork.

The problem is, you make the big decision to spend £700 odd to have your car and subframes dipped, then they hit you with the electropriming treatment option thingy which is another 800 odd quid. Naturally you throw up your arms in horror and politely decline, when the long term sensible decision is to say, "Yes please!"

[Giff]

SPL use a seperate comapany to do the E Coating who are winding down which means they won't be able to offer that service at all.

[mk1]

I am still STRONGLY of the opinion that most, if not all acid dipping processes are not what they are cracked up to be.

As far as SPL are concerned I know for certain that the "E-Coat" treatment that they use does not penetrate all cavities etc, like they claim it does, it is also pretty well proven that once treated cars are finished some of them start to "bleed" rust & acid from spot welded seams.

When you think about it, immersing a complex metal shape in a big vat of acid then hoping that you are going to get it all off is simply daft!

If you MUST remove all paint from a car, blasting is still a much better option. At least the car stays dry & acid free.

[YMJ]

I am still STRONGLY of the opinion that most, if not all acid dipping processes are not what they are cracked up to be.

As far as SPL are concerned I know for certain that the "E-Coat" treatment that they use does not penetrate all cavities etc, like they claim it does, it is also pretty well proven that once treated cars are finished some of them start to "bleed" rust & acid from spot welded seams.

When you think about it, immersing a complex metal shape in a big vat of acid then hoping that you are going to get it all off is simply daft!

If you MUST remove all paint from a car, blasting is still a much better option. At least the car stays dry & acid free.

agreed!

[andy1071]

I think that in theory, the acid dip process should be ideal, as it gets rid of/kills all the rust.

But (and it's a big 'but'), isn't the problem that you have a completely unprotected shell until a suitable coating is applied to protect it?
-If the shell is shipped to another company (for e-coating or whatever), then it must be exposed for some time (days?), and rust will start again immediately? -Their video shows the bare shell being moved around outside by a fork-lift.

If you take it away to repair it, it will rust.

Plus, all the weld seams, which are pretty much guaranteed to have had some rust in them, pushing the joint open, will have perfect crevices to collect the acid, and water, and anything else (and will start to rust as soon as you look at them -or even before).

The e-coat ( Electrophoretic Coating ) will not work in the cavities, because it relies on the paint being 'charged' and the bodyshell being connected to an electric supply to attract the paint. -Have you noticed that plating and chroming don't get into hollow areas very easily (and these are open!). -If it did work properly in the cavities, you wouldn't have to wax inject, as they recommend.

So. I have realised that I'm agreeing completely with Mark
-Blast it (there are some very gentle blasting media available that won't destroy rust thinned panels) treat it, paint it, then wax it regularly.

[YMJ]

apparently the BSI standard time between blasting and anti-corrosion treatment is 6 hours max, if that is any use?

[Giff]

Doesnt the residue from soda blasting afford a level of corrosion resistance for quite some time?

Similary the solution used to wash off the acid after dipping?

[Gray]

and the e-coat company is just next door I believe.

[Tim]

Aren't the replacing the e-coat with an electroless nickel coating now?

Tim

[mk1]

Alkali solutions will provide some level of protection for a while, but to give any level of "real" rust protection you need to use something like Zinc Phosphate. This however is what was used in the original BMC rotodip process & we all know how well that worked don't we

[Giff]

I was meaning just a bit longer than six hours, I wasnt hoping that a bit of bicarb dust would let it survive in the ocean

[Tim]

The local soda blasting guy here has a car that he's completely stripped on one side and still in shiny paint on the other side, that he takes around shows. I saw it 9 months after he first did it and it was still bright. It would have needed a wipe over with metalprep and some silicone remover, but was otherwise ready to paint. He said that he hadn't done anything to the surface after blasting it.

Tim