Paint prep

[Davemate]

Are electric palm sanders ok for buzzing over a car before painting ?
Hopefully the wife's herald is going to get a blow over next week and I want to give the car a quick sand over before it goes in.
The bodywork is solid,but the whole car is covered with what looks like stone chips that have then gone rusty.
I was thinking about buzzing the whole car(rusty bits only) to get rid of the rust then useing rattle cans to cover them all back up before it gets sprayed.
My saloon has been sprayed white but that is flaking off so I want to also use the palm sander to remove all the white to reveal the green underneath then that can be dusted over as well.
So electric palm sander £20-30 or should I get an air sander ?
Also I am considering the noise factor as I don't want the compressor on continuously, I like my neighbours and a palm sander may be a damm site quieter

[Clive]

Dave, what are the sprayers doing? Is the prep all down to you?

The leccy palm sanders are not great for fine finish work. It really needs to be a DA version if you get one, NOT orbital.

Best bet is to do it by hand. Rust chip areas need serious attention, so a fine flap wheel in a grinder, or a wire brush?  Get a rattle can or 2 of etch primer too, as that helps kill any rust and "bites" into bare metal. Acid 8 is very good. I would also suggest acrylic stopper (not cellulose as that shrinks far too much) to fill the surface imperfections.
Hopefully the sprayers are using a decent 2k primer/filler and flatting?? that will help a lot. If you are flatting, use 600 or finer (I use 800) wet/dry paper, anything coarser will mean the finish will not be great and never shine well. You will be surprised how fast you can flat the car back, a few hours (hopefully) by hand should do it. Plus you find all the bits you want to sort out.

My post appears rather rambling...... :B

[Davemate]

Clive,
  All the sprayer is going to is dust it over.
The wife has said I can't touch my cars anymore until hers is sprayed.
I just want it all one colour and a mate of a mate will mask it up and "hit it" for a couple of hundred quid.
So I just want to give the car a bit of a chance to look ok ish for a couple of years until I can afford to do it properly.
This is what I have to try and sort out,the sprayer has said he can do it but then the cost goes right up and as I said if it can stay looking ok for eighteen months to a couple of years I'll be we'll happy

[James]

I'd ask the sprayer what they want or expect you to do.

As Clive says a proper DA — you can get one from Car Spares :)

Probably cost <£150

Also get the decent primer Acid 8 too — think thats less than £20 a rattle can.

Don't skimp on prep :)

[Alex]

Dave you need to be aware that air sanders use an awful lot of air!
If you don't have a very big compressor you will always be playing catch up.
I have a small 50 litre compressor and it won't run my air sander for more than a couple of mins before stopping I then have to wait.it means the compressor runs constantly!

Your areas needing the most attention do appear to be localised......do it as Clive says,by hand.
At least that way you'll retain the original base protection.

[Richard B]

Alex wrote:

I have a small 50 litre compressor and it won't run my air sander for more than a couple of mins before stopping I then have to wait.it means the compressor runs constantly!

I think is more to do wih the flow rate of the compressor rather than the capacity of the resevoir.

My 50 litre compressor has a CFM (cubic feet a minute) of 9. Ideally something over 13CFM is best for running air tools long term.

[Mark Hammond]

Prep is everything, get this right and you'll have a paint job that'll last longer than 18 months or 2 years.  As Clive says, a DA is the best, but by hand can be just as good too.

M.

[Clive]

I have used a sip DA, AND MY 3HP COMPRESSOR STRUGGLES. bORROWED A cp VERSION, AND IT COPED WELL.
(AND my fingers are too fat, apols for caps lock....)

Think leccy DA's are available. Not cheap. But for what you want, I would go hand-sanding.
http://www.ebay.co.uk/sch/i.html?_nkw=DA+sander+v&_sacat=0&_odkw=DA+sander&_osacat=0&_from=R40

Do get some acrylic stopper. Really, it is a revelation......
I got some locally for about £7. Not a big tube, but used about half doing a herald. And I kept finding lots of tiny imperfections as I went along. Got most of them...

[piman]

Hello Dave,

there's quite a bit of rust there, and I'm sure you'll find more under the paint. The best way to get rid of that is to use a strip and clean disc on an angle grinder. http://solutions.3m.com/wps/portal/3M/en_US/Marine/Home/Products/Catalog/?PC_7_RJH9U5230GE3E02LECIE20S4K7000000_nid=GSLFNJGWJ4beRJ5GMFSMV0gl (this link is just to show the disc, generally available at engineering merchants, welding suppliers, farmers merchants etc.)

A DA will get rid of the rust eventually, and as suggested electric ones are expensive. By hand will take a lot of hard work and patience. These discs remove even pitted rust quickly (Which a DA won't) and leave a finish good enough to prime.

Alec

[Clive]

Hmm, looking again I would agree the valance will require a power tool  8) The stip-discs are awesome but expensive. Angle grinder with wire brush is also very effective, I would probably use that on the valance and end up at bare metal. Rattle can of acid 8 and let him stonechip the thing. Bonnet looks more like small stonechips, probably needs only small area cleaning up and a dab of primer plus a smidge of stopper. Not sure about the rest of the car.

BTW which colour has the lady chosen?

[Davemate]

The colour will stay as near as possible to what it is now.
It's supposed to be cactus !

Alec the whole car is covered with bits that look like the front valance,only on a smaller scale.
The metal is very good,it just has a very light rusty coating.
It may well end up just being flattened back by the painter then sprayed.
I hope to have my garage/workshop built within a few weeks and I can then do my saloon properly and my herald,as her car will have been done there is nothing the wife car complain about  ;)
Then later this year I can redo her herald in any colour she likes as I can strip the shell out and spray the inside along with the door shuts

There is sense in my madness

[piman]

Hello Dave,

just flatting back will be very slow in removing the rust, even with a DA sander, and there is little point painting it without getting back to bright steel. These discs remove paint and rust very quickly, especially as you only need to do the localised spots. Buy one and try it on an old panel or the like, I think you'll be impressed?

I've done bare metal resprays in the past (I don't think these were available then) and used a DA and a palm sander to remove the old paint, a slow and tedious job. The next one I do I'll use these discs to remove the paint.

Alec

[James]

Dave — those discs Alec mentions are really good.

Get the rust off quickly and properly and it'll be worth it.

Otherwise it'll be looking shabby again in 6 months when it all comes through.

Nothing worse than fresh paint bubbling up — it'll look worse than the "patina" it has now.

[Spitfire2500]

jcarruthers wrote:

Get the rust off quickly and properly and it'll be worth it.

Otherwise it'll be looking shabby again in 6 months when it all comes through.

FWIW agree with James and piman. Get it back to bare metal, get rid of the rust before priming and painting. If you just flat it and paint over it the rust will be breaking through again in no time.

I suspect your rust spots will be a mixture of chips and also areas where the paint has aged to the extent that it's allowing moisture through to the metal.

I'm doing exactly the same with bits of my Saloon where wholesale panel replacement isn't required. Takes no time at all to get back to bare metal using angle grinder with wire cups and flap discs. See this (none of which were stone chips) http://bigsixaddiction.blogspot.co.uk/2012/12/cleaning-up-well.html -- now that I've sort of got the hang of what I'm doing going from the first pic to the second pic should only take a couple of hours.

Flap discs not necessarily that expensive:

I'm using these -- http://www.tooled-up.com/Product.asp?PID=143476 -- and these -- http://www.toolstation.com/shop/Power%20Tool%20Accessories/Power%20Sanding/Flap%20Discs/d80/sd1790/p87752 -- in 40 or 60 grit to remove paint and rust -- and these (which are expensive but last for ages if only used for finishing after removal of paint and rust) --http://www.tooled-up.com/Product.asp?PID=132512 -- for finishing prior to degreasing and priming. Other options are of course available  :X

After priming I'll be overcoating with Triumph White celly from a can to seal off the primer and when I'm be done I'll get a paint shop to respray the whole thing and finish it off properly.

[piman]

Hello Bill,

in my experience cup wire brushes, even the knotted more aggressive ones do not remove rust properly, and flap discs tend to clog up if used on paint for any length of time. Flap discs are excellent on bare metal however. That is what is so good about the strip and clean discs, they do not clog when used on paint. They do not last very long so are expensive but the time saved and the excellent result make them worth while.

Alec

[ferny]

I like how we all have different methods.


Those discs Alec uses are great, but last all of two seconds. They also don't like the original red coating Triumph used on some panels and rather than removing it just push it about.

I don't like wire cup brushes at all and only use them as a last resort. Instead I much prefer knotted wire wheels. I find them far quicker and much more precise.

Flap wheels are excellent but extremely abrasive. I only use them to clean up and shape welds. They go through metal like butter.



My choice for your car would be to whip it all back with a knotted wire wheel where needed and then hand cut the good paint back to get years of shit and grime off. It'll also show you where the paint is bad enough to also require fully removing. Then I'd degrease and go back over the clean metal with one of Alec's pads or another clean knotted wheel to get the metal shiny silver. After that I'd coat it all with Hydrate 80 (probably worth getting your painter to test it first to see if it reacts with what he's using).

Anything less than all of that and the car will look shabby and shit within weeks of painting. Spend an extra day or two now getting it right and that job you want to last two years will last longer saving you sheds loads of work removing newer paint later on. Don't forget to pay special attention to panel joins and folds as if there's any grime or rust in there when you paint it'll fuck up the whole job.

[Spitfire2500]

piman wrote:

in my experience cup wire brushes, even the knotted more aggressive ones do not remove rust properly, and flap discs tend to clog up if used on paint for any length of time. Flap discs are excellent on bare metal however. That is what is so good about the strip and clean discs, they do not clog when used on paint. They do not last very long so are expensive but the time saved and the excellent result make them worth while.

To be honest Alec I haven't tried the strip and clean discs yet but it sounds like I need to give them a go -- I've got a lot to do  ??) When I started cleaning the front end of the Saloon up I just played about with what I had lying about in the garage. It works but needs at least two passes -- cup brush to get most of the paint and rust off (they don't clog), then flap discs to get the last of the paint and rust off. Sounds like the strip and clean discs could save me a lot of time.  

[Spitfire2500]

ferny wrote:

Instead I much prefer knotted wire wheels. I find them far quicker and much more precise.

That's interesting. I hadn't considered using them on panels -- I thought they might be too rough. Sounds they're worth trying out as well  :)

[ferny]

Our panels are nice and thick so it's fine. I even used them on the alloys and it was fine;