Classic cars forum & vehicle restoration.

[petermeachem]

I don't wish to go over old ground but I don't understand the level I need to go to.
My car had lots of surface rust spots. Eventually I decided it was probably easier to take all the paint off rather than fiddle about.
I peeled most of the paint off with nitromors which was pretty easy, didn't take too long at all.
Interestingly it then seemed to be a lot more rusty than it had been on the surface. There was spider rust too, very interesting and organic like little rusty rivers. I went over it with a poly disc (this must be one of the best tools ever) and the large areas disappeared and I had lots of little pits.
Then I painted the whole thing with phosphoric acid (milkstone remover). I have 5l, 1l would have been tons.
I had read that the pits would go black and the rest grey and that the grey is ok to paint over. I don't think mine would. It wasn't just a passivated surface which was what I was expecting, but was fairly thick and remained sticky.
If it was ok to paint should you not prepare the metal like for painting before applying it? I.e degrease and wipes. Otherwise might you not be painting on a dodgy substrate?
Anyway, I poly disced the whole lot off this morning and reapplied acid. I went over it with wire wool but that didn't shift anything the polydisc wouldn't.
At that point my drill broke (bang, cloud of smoke) so I washed the car down, dried it, went over it with meths to help the water off and then wiped on something called Gibbs Brand which is supposed to stop it rusting.

Am I ok to poly disc and then acid the pits?

I've ordered a disc for my angle grinder, in the meantime I have all the fiddly bits, moulding, window frames etc to do where the disc won't go.

Am I going in the right direction? I want to get all the paint off, do some small repairs and then spray an epoxy primer. That is going to take a little time to get to paint stage.

[ukdave2002]

Hi

I use phosphoric acid on all bare metal prior to painting, wether it looks rusty or not! Rinse it off after 20 mins, then clean the panel with solvent wipe (panel wipe) wipe with a tack rag then paint immediately.

All of this should be completed with minimal time between the processes.

Any loose rust should be removed first, your poly disk is ideal for this.

Dave

[colwyn500]

Peter, I have recently been through this and did fairly small areas at a time. The process isn't as straightforward as it seems.

Once the paint was removed I went over the whole lot, by hand with 60 grit sandpaper.

Then I applied the acid and rubbed the "spidery" areas with stainless steel scourer pad, scratched the pitted areas with a pointy screwdriver and very stiff, manual wire brush. The spidery stuff mainly wiped away quickly. The pits needed several applications until the layers had gone and I could no longer expose brown rust. I found it useful to do the occasional light spray with water and then to rub the area again.

Eventually I had to compromise for sanity's sake and say to myself "That will do".

I then rinsed with water and wiped with paper towels.

There is still a residue, mainly the white salt of un-neutralised acid which should really be removed; I found a product to do this.

Then a wipe with isopropyl alcohol or similar solvent and you're finally ready...it takes ages and my car is tiny.

Thread here with photos. http://www.oldclassiccar.co.uk/forum/phpbb/phpBB2/viewtopic.php?t=13107&postdays=0&postorder=asc&start=210

[Bitumen Boy]

I've also had the problem of small areas which phosphoric acid - or any other chemical I've tried - won't touch, almost as if they're greasy though how I can't imagine. Luckily they have only been small, and what I've done is to sandblast them off, a very messy and wasteful job which I do as sparingly as possible! It does, however, do a very good job of getting these problem areas back to an absolutely bright surface. Maybe the "recycling" type sandblast guns would be good for this sort of work, but mine is the total loss type so I do it outside in the back lane on a dry day. I gave up buying expensive grits and now use ordinary builder's sand dried in the bottom of the oven a little at a time, know the dust isn't supposed to be very good for you but there's usually enough of a breeze to blow it all away...

[petermeachem]

colwyn500. I've followed your article with interest and amazement. I don't want to get too anal about rust pits but I don't want my paint to fall off either. I suppose the ideal is to get to a stage where we have just iron phosphate and not iron phosphate on top of iron oxide.
A poly wheel will only plane the surface flat. I can't see a wire brush getting much further down either. I'll have a poke at the larger ones and see if I can dig the phosphate out. Tiny pits I shall leave.
I've been googling this and there is a huge amount of conflicting advice. I suspect that they are all mostly ok. I can't find any research results, it would make a pretty good PhD project except you would have to wait for years to get results.
My car is also tiny thank goodness. I keep looking at the yawning acreage of the front wings which also have two sides, not looking forward to doing those much

[colwyn500]

This statement:
"I suppose the ideal is to get to a stage where we have just iron phosphate and not iron phosphate on top of iron oxide."
Spot on in my opinion. Good luck Peter. What car is it?

[petermeachem]

Austin Seven Ruby. It splits quite nicely into separate jobs. Once you take the doors bonnet and wings off and it has full length fabric roof half of which is sunshine, there isn't a huge amount of body. Just as well

[D4B]

[petermeachem]

I've just been going over it with a small wire brush, a copper one originally used to make your Hush Puppies look lovely again. I never throw anything out! This worked really well. A lot of the little spots of phosphate are now clear. They don't seem to stick to steel very well, more of a crusty coating. The deeper ones I picked at with a dental tool (I've no idea why I have dental tools), the sort they scrape plaque off with. This was ideal, a bit like this http://www.petstore.com/media/catalog/product/cache/1/image/619x800/9df78eab33525d08d6e5fb8d27136e95/C/l/Classic-Products-Tooth-Scraper-Tartar-Remover-6-1-2-Inch-99.jpg
Nice fine very hard and sharp point.

I have to fix my garage promptly. It was tipping down outside and raining quite hard inside. It's a Marley with a corrugated asbestos roof. Rain was coming in where the sheets overlap and running along a roof beam. I need to get up on the roof (gingerly) and sweep any moss off. Not ideal.

[Phil - Nottingham]

I did a whole door panel like that in 1994 just by brushing on liquid Jenolite. I broke the car in 2010 and paint on the door is still good
_________________
Rover P2
Rover P4
Rover P5 & P5B
Land Rover S2 & S3
Morris Mini Traveller Mk2

[petermeachem]

15 to 20 years will do me fine I think

[colwyn500]

[petermeachem]

1st Dec 2034 would be cool, it will be 100 years old.

[ukdave2002]

[ukdave2002]