The Spray Painting Thread

[ian]

best thing to do is ask you local panel shop who there suppliers of equipment are
as they get trade prices , then ring the supplier and tell them you are from TERRA OPERATIVE PANELS and would like some prices and would like to open a cash account
that way you can order all you paint and panel stuff at trade prices and then pay cash for it
ian

[TERRA Operative]

Good idea. I do have an ABN and business name (B3Motorsports) which I can use to do as you suggest, I might try it.
I did find the Devilbiss Gti Pro for sale for $500 at Brisbane Refinish Supplies, is this a decent price?

[love ke70]

try harts
theyre in slacks creek.

http://www.hotfrog.com.au/Companies/...Paint-Supplies

they looked after me well and my panel beater swears by them

[TERRA Operative]

Well, I splurged, and my bank account is looking a little worse for wear....



I ended up with a DevilBiss Gti Pro Base HVLP gravity feed spray gun with air adjustment/valve, and a Kincrome hard case for it all.

Now for the paint......

[Hurricane]

good thread to read hear, goin to be watching this now

[1975ToyotaCrown]

TAFE Colleges are a great place to start.

[Screamn_Sleeka]

my experience:
Abrasive methods dont do anything for rust repairs as you leave paint covering the rust. Also, if you hit metal when sanding you remove the zinc phosphate rust preventative coating and if you paint the area without re-applying zinc phosphate rust will accelerate. Sanding a car is therefore not a good idea if you want to keep the car for more than 3 years after painting it.

Chemicals methods , paint stripper (DCM, Methyene chloride, trichloroethane etc), gets all the paint off and softens bog (this is a good thing, dont know why the other guy was baggn it?) If there is bog on a car, there is generally rust underneath, even if it was just a ding the surface of the metal has cracks in the brittle zinc phosphate and rust will accelerate. However it stinks, very bad for you, and a drop in the wrong place is irreversible. Zinc phosphate treatment is not needed if there is not rust/expose steal. (Steal is shinny, zinc phosphate coating is dull).

Sand blasting (particle blasting), silica, walnut shells etc. This is a quick method to remove paint from metal, it does etch the zinc phosphate and steal so zinc phosphate treatment is advisable but not as important when sanding. The etched surface is ideal for painting giving optimal bonding properties. However, it makes a huge mess, everything is covered in dust, you really need a booth for this to work well. Its also the most expensive method as you need a sand blaster (pot and gun) and a decent compressor.

For taking a car back to bare metal for a quality spray job, chemicals or blasting should be used. Unless a full booth is available, blasting will make too much mess to be feasible so the average man at home is better off with the paint stripper chemicals. An organic chemical filter mask will reduce the risk of cancer and goggles will reduce risk of eye problems.

[o_man_ra23]

Where do you get the idea that a scratch in the zinc coating will accellerate rust?? The zinc is a sacrificial metal, and will always corrode first. Also,if you paint the car properly, then the steel will be isolated from all oxygen sources, and thus won't be able to rust anyway.

The problem with softening the bog is that all the prep work needs to be re-done. Cars come from factory with a certain amount of fill in them, this is because the panels arent perfectly straight. If you kill all this, you will either need to re-do the fill, or you will have a wavy car. So chemical stripping and sandblasting is only good for bare metal sprays. And chemical stripper has too much danger of causing rust to use in any fine areas, so it becomes an unuseable product in reality. Soda blasting is your other option.

So yeah, if your doing a re-coat... sand the bastard. If your going bare metal, sandblast or soda blast. If you want the car to rust like a holden, chemical.

[Screamn_Sleeka]

Where do you get the idea that a scratch in the zinc coating will accellerate rust?? The zinc is a sacrificial metal, and will always corrode first.

Exactly, so if you scratch the zinc away the steal will fast faster than if it wasnt there.?!?!? you are proving my point.

Also, if you paint the car properly, then the steel will be isolated from all oxygen sources, and thus won't be able to rust anyway.

No that is wrong, paint a car as well as you can and park it out side in the weather and it will rust, this is from practice not assumption. You can not isolate oxygen, physically impossible. you need a protective layer under the paint, sanding removes that layer.

The problem with softening the bog is that all the prep work needs to be re-done. Cars come from factory with a certain amount of fill in them, this is because the panels arent perfectly straight. If you kill all this, you will either need to re-do the fill, or you will have a wavy car. So chemical stripping and sandblasting is only good for bare metal sprays. And chemical stripper has too much danger of causing rust to use in any fine areas, so it becomes an unuseable product in reality. Soda blasting is your other option.


Ive got not idea what you sources are, but no cars come with wavy panels, thats the effetcs of a few years of the stress/strain put on the them from driving. Factory cars have a thin layer of primer NO FILLER. Robots paint cars, not humans, there is not filling and no sanding. The layers of paint are equal all around the car, any 1st year forensic can tell you that.

How can chemical strippers cause rust? it takes the old paint off and then you replace it will new better paint?

So yeah, if your doing a re-coat... sand the bastard. If your going bare metal, sandblast or soda blast. If you want the car to rust like a holden, chemical.

I have practical knowledge, you clearly don't and the difference is obvious. Blasting is a good option but to facilitate the mess is beyond most people situations.

[Rcubed]

o_man_ra23: Have too.
Screamn_Sleeka: Have NOT!
o_man_ra23: Have too.
Screamn_Sleeka: Have NOT!
o_man_ra23: Have too.
Screamn_Sleeka: Have NOT!

Ladies please!! clothes off and into the jellow!

Let me state from the outset, I know Jack Schitt about spray painting!

i'm surprised that there would be a sacrificial metal coating on a panel. So I got out my Toyota 'Fundamental Painting Procedures' [pub.no.36438e - printed 1984] for a bit of a read. section 4 refers to automotive paints and under 'primers' is the following excerpt [which i've abbreviated]:
'1 Wash Primer
Wash primer is usually called etching primer. ... The principal elements are vinyl butyral resin and chromate zinc (type of rust prevention pigment) with phosphoric acid added as a hardener. When applied directly to metal, an anti-corrosive chemical pre-treatment coating is formed.' page1-13

most rust treatments i've used have had phosphoric acid to react and form a non-reactive layer.

my [verbose] point here is IF you expose bare metal don't you just use an etch primer???

[love ke70]

ta23 yes

and secondly, sand a panel then use de-ox-it. its like 25% phosphoric acid and turns metal blue...stops it rusting

[o_man_ra23]

Screemin Sleeka, you just have NFI do you??

Remove a tiny bit of that zinc, and the panel MAY rust EARLIER not QUICKER, all the zinc must be gone first.

Robots don't always paint cars. Modern cars may have smoother panels, but seriously, who is going to respray a modern car themselves?? You would have to be a dickhead to attempt it. In China and India (and other such places) cars are still painted by hand. They do use electrostatic methods to ensure the paint all sticks, but it is still done by hand.

Back when my car was painted, panels were pressed with heat in a mould. They came out pretty darned good, but not perfect. There is a certain amount of tolerance, and that tolerance becomes wavy once people on the assembly line put the pieces in place and weld them together. Thus the need to fill the cars before painting.

It has been proven that paint will protect. An experiment was done (an engineering experiment, not a forensic one... you probably won't accept it though) where 2 steel boxes (yes, STEEL, not STEAL, you can't even spell the alloy your talking about - so how do you think you know anything about it??) were both painted with the same compound, and put into a common tank of salt water (I believe it was actually sea water, being a great electrolyte with many different chemicals in it). After a few months, neither had signs of corrosion. One box was lightly scratched. 2 days later, the scratched box had rust forming all over it, including areas which did not have the scratch. This proves 2 things. First is that rust is transferable within steel. Second is that a properly painted steel object won't rust if there is no breaks in the paint's seal. Thus your using shit paint.

And yeah, TA23 is definitely right. Zinc is added after the metal is formed, sometimes by electrolysis, sometimes by spray addition. Either way, if your REALLY worried about scratching the surfaces, use etch primer (which you should in any areas which have been sanded back to bare metal to improve adhesion anyway)

Oh, almost forgot. Chemical strippers are a harsh alkaline. If you don't remove ALL of it, because the alkaline contains hydroxyl (OH- or Oxygen and Hydrogen bonded together with a loose valence electron on the Oxygen atom) the oxygen now has an easy method to react with the steel. Thus you get H2 molecules free floating, and the oxygen disappears into the metal. Paint also doesn't stick to the chemical stripper, so you open a hole in your protective coating to allow more oxygen in.

Don't know where your sources are, but I would guess that they originate up your arse.

[JP]

for the guys who spray 2-pack, what respirators do you use?

Have been looking at the Devilbiss air-fed full face mask

[ian]

hi jp
its not just a matter of getting an air fed regulator
you need a drier separator to go with it
as just using a feed from your air compressor, is not only illegal it is highly dangerous
air direct from your compressor has oil in it
have a look at the shit that comes out when you open your drain tap on the tank , you would not want that in your lungs
i am not sure what the regs are in QLD but i had to do a short course in air fed respirators , very similar to the one that the fireys do
ian

[JP]

Thanks Ian,

I'm aware that they need the appropriate filter too, for the Devilbiss they recommend the DVFR-2 as a minimum: http://www.itwfinishing.com.au/profile.php?product=43

I'll look into the QLD regs and see what courses are available.

Jason