Subframe scrape repair - 3M schutz or Frost Chassis paint

[74hc04]

I've had a bit of a scrape to the subframe of my Citroen C1 last weekend (shouting match with the other half over whether or not I can park on that raised curb - you get the picture!)

My first attempt to get the job done before the rust started involved zinc rich primer followed by U-Pol stonechip. The stonechip cracked to a "crocodile skin" finish so has been wire-wheeled back to steel this weekend. I'm guessing that the paint reacted with the primer or it was something to do with poor adhesion to the zinc, anyway...

I have now painted two coats of an ordinary white acrylic primer and have the choice of two top coats. A can of 3M 08861 Schutz - painted by brush or an aerosol of Frost Extreme chassis black which should arrive on Monday. A friend swears by Schutz as he uses it, straight to steel, on his Land Rover chassis after welding.

I have brush-painted the Schutz to a piece of cleaned-up scrap steel and, 3 days later, I am not impressed. It can easily be scratched-through with firm fingernail pressure and I am unsure whether it will ever harden any further (or worse crack and fail to seal). One half of the scrap steel has primer, the other doesn't - it seems to make no difference the Schutz. (Yes I do appreciate that this should be applied with a proper Schutz gun).

Any opinions about either of these products would be appreciated. There is a little surface rust elsewhere on the subframe (MOT searches suggest that these all get like that after a while) and I am not looking for concours condition, I just want to get back where I started.

I am pulling my hair out at the thought of another week on the bus with the car in the garage! I know it's not a PH-worthy car but it's still my pride and joy!

Thanks in advance.

Edited by 74hc04 on Saturday 4th November 10:05

[steveo3002]

get some epoxy primer like jotun jotamastic ...hard as nails and will go over any prep work

schutz is meant to stay soft and be sprayed on , mostly used to cover up mot bodge work

[227bhp]

I would have left on what you did originally or put even more on after it had dried properly. Does it matter what it looks like as long as it does the job?

[74hc04]

Thanks guys.

I don't care what it looks like as it's out-of-sight. So long as the MOT man doesn't jump up and down it's fine.

The problem with the "crocodile skin" finish was that you could see the grey primer through the cracks. I wasn't confident as to how well it had adhered either.

The car is almost exactly 6 years old. If the subframe lasts another 3 or 4 years, I will be happy enough.