Classic cars forum & vehicle restoration.

petermeachem · Joined: 23 Sep 2013 Posts: 358 Location: Chichester Sussex

As the house is pretty well sorted I'm keen to get on with the car. Too cold in the garage so I thought I could clean up and paint lots of bits and pieces in the conservatory, shock absorbers, radiator side panels, running boards, bumper irons etc.
Not sure what to use. I used epoxy primer on the body, but that will be awkward to mix accurately in small quantities and I am bound to make too much and waste it or too little and run out. Not sure how well it brushes either. Most of the parts that need doing end up underneath the car so I need a good tough layer to stop rust and end up with black and shiny. Brush or spray can would be ok.
Any suggestions?

goneps · Posted: Sat Jan 24, 2015 8:30 pm Post subject:

I find POR-15 good for such applications. Leaves a smooth, hard gloss finish when brushed on, and according to the blurb works better in cold and damp conditions. Applied directly to bare metal. Best for underneath applications because it dulls when exposed to UV for long periods. Available from Frosts in Britain.

Richard

petermeachem · Joined: 23 Sep 2013 Posts: 358 Location: Chichester Sussex

I thought that was anti-rust? The parts are derusted and coated in phosphoric acid already

Ah, do you mean this? http://www.frost.co.uk/automotive-paint-coating-electroplating/automotive-paint/por15-paints/por15-blackcote-paint.html

goneps · Posted: Sat Jan 24, 2015 9:36 pm Post subject:

No, I just use the good old standard stuff for chassis & running gear parts. Saves messing about with primers and other treatments, providing a durable finish for the least bother. I've always used it straight on bare metal, either wire-brushed or sand blasted. For instance:

This is a single brushed coat on the wire-brushed bare steel.

ajlelectronics · Joined: 04 Oct 2010 Posts: 168 Location: Gloucester

Superb paint, designed for the job. However, it is not good on clean, shiny bright metal and unless prepped, may have the paint coming off in sheets. So, for nice metal, etch primer. For rusted, pitted, weathered metal, POR-15 can't be bettered. Most of the complaints you will hear are due to it being used on fresh metal, by people who didn't bother to read the information.
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ukdave2002 · Joined: 23 Nov 2007 Posts: 4240 Location: South Cheshire

petermeachem · Joined: 23 Sep 2013 Posts: 358 Location: Chichester Sussex

Well you can actually. It turns rust black, I ground pretty much all of that off. The acid does a pretty good job of preventing the bare steel from rusting. I understand that it can be painted over but that seems a little iffy to me so I shall take it off and paint clean steel

ukdave2002 · Joined: 23 Nov 2007 Posts: 4240 Location: South Cheshire

Peter

Phosphoric acid simply changes rust (iron oxide) to ferric phosphate, the black stuff.
The ferric phosphate will provide a limited degree of corrosion protection, but once its removed you are back to plain steel, and of course if there was no rust in the first place there wont be any ferric phosphate...

The ferric phosphate needs to be removed prior to painting as it can be loose. When I painted my bare metal MGA shell it had been acid stripped back to bare metal, kept bone dry for a couple of weeks and it looked fine, I still coated it with phosphoric acid before painting and was surprised how much of the steel had a black shadow, as soon as bare mile steel is exposed to the atmosphere corrosion starts.

I'd have probably got away with using an etch primer, but was happier coating with phosphoric acid just prior to painting.

Dave