The Spray Painting Thread

[o_man_ra23]

You can buy Iso-Cyanate free 2-pak which only requires a decent dust filter, rather than the full respiration equipment. My plan was to have a mask with 2 pipes directly through the roof/wall of the shed, each with an opposing 1 way valve, such that one pipe is for breathing in, the other is for breathing out. Not sure if this complies to standards, but would be quite sufficient for doing only a couple of cars in your life no doubt. Obviously dust filtration is still required. Forced air can be achieved by a small fan blowing through that pipe... excess that is not breathed will go back out the exit pipe anyway.

Note that this method probably doesn't meet Aus Standards, but then again I don't think too many home booths will.

[twentyEight]

My plan was to have a mask with 2 pipes directly through the roof/wall of the shed, each with an opposing 1 way valve, such that one pipe is for breathing in, the other is for breathing out.

You only need a respirator (about $60 for a 3M one with both a particle, and vapour cartridge) if you're using iso free 2K... Your idea is just silly!

[love ke70]

or just risk it, the amount of chemicals we are exposed to in a lifetime, a car or 2 of 2-pak cant be too bad.

i mean, how many of you use respirators or even a dust mask when you cut MDF?

[JP]

what iso-free 2-pack brands do you guys recommend? Want to use toyota's new Graphite metallic grey colour on one of the cars I have here to spray.

[o_man_ra23]

You only need a respirator (about $60 for a 3M one with both a particle, and vapour cartridge) if you're using iso free 2K... Your idea is just silly!

Depends if I can get the colour I want in iso free brew

As for suppliers... ring around every paint shop in the phone book and ask them what brands they have of iso free, and how much it is, and what range of colours they can do (especially ask them that if you already have a colour code... go to a dealer and take down all the details of the car, and the colour code)

[twentyEight]

Just don't go for a solid colour! Only the Clear in a COB system* contains iso...


*or Single Stage systems which only come in solid colours... (Unless you're stupid like Ford and Holden and try and create a metallic and pearl version - ie. EAs and VNs)

[GT1978]

Is there anything special about cleaning fiberglass/gelcoat prior to painting? Can I just use prepsol or will this desolve the gelcoat?
Seems I have got my grubby hands all over my spoiler.

Glen

[o_man_ra23]

Can't imagine Prepsol to dissolve gelcoat... but best to check. Maybe try Google??

[oldcorollas]

just to clarify an earlier point...
zinc is not the same as zinc phosphate

zinc galvanising is a solid layer of zinc metal. this is a sacrificial layer, and yes, you cna have a large area of steel exposed but it will still rust.. just not as fast as if the zinc wasn't there.

if you scratch a steel coated with a phosphate, the scratch will still rust... i am not 100% sure, but i don't think the phosphates are sacrificial.
from random sites

Zinc and iron phosphates are deposited electrolytically to form an inhibitive layer over the metal. They "passivate" the substrate so that, in the presence of moisture and oxygen, galvanic corrosion cannot take place. You can think of zinc and iron phosphates as functioning like an insulating blanket, preventing iron ions (Fe2+) from dissolving into the surrounding electrolyte. Zinc-rich primers (organic or inorganic) are intended to corrode in place of the expensive substrate, in this case, steel. Hence zinc is called a "sacrificial" anode in the corrosion cell.

In summary, zinc rich primers contain metallic zinc particles, and prevent corrosion by means of "cathodic protection". They are always applied directly over steel to maximize the electrical conductivity between the two metals. This is very different from inhibitive primers, such as zinc chromate, which forms an inhibitive "blanket" over the metal preventing iron ions (Fe2+) from dissolving. They are usually applied over pretreated, conversion-coated surfaces, such as iron or zinc phosphates. Here the conversion coating provides both corrosion resistance and adhesion between the substrate and the organic primer.

Phosphating, often referred to as conversion coating, is the application of iron or zinc phosphate to a ferrous or non-ferrous substrate to produce a coating, which forms a uniform, chemically inactive surface. This coating inhibits corrosion of the substrate metal and improves paint adhesion.

going by that, if you have a scratch in an insulating layer, then it will rust even faster (locally) than if there was no insulating layer...


paint doesn't keep oxygen out. paint doesn't even keep water out 100%. and there are always "holidays" after painting, so there will always be rust.
paint still does reduce the amount of oxygen, and greatly reduces the water at the metal surface... and you need both to have a corrosion cell

[ian]

Is there anything special about cleaning fiberglass/gelcoat prior to painting? Can I just use prepsol or will this desolve the gelcoat?
Seems I have got my grubby hands all over my spoiler.

Glen

prepsol will not harm gelcoat
we have made fuel tanks for boats out of f/glass that held some pretty exotic brews
ian

[Sparkys]

Wow! I just read the entire thread, lots and lots of great information here! Kudos to those who have painted their own cars, it's a great fun and rewarding process. I've done 5 and working on an R32 at the moment, but my TA22 will be the biggest project so far.

I have a couple of quick questions for those in the know.

1. I bought a new compressor, it's got a 116L tank and a 3 hp, 15 amp motor. This is more than capable of handling my home painting efforts as well as the infrequent use of a rattle gun/air driven tools. Is it enough (with the appropriate dryer/filters) to run a spray gun and an air fed face mask?

2. I have decided to strip the paint from my TA22 with two methods. I'm getting the engine bay, interior, boot and inside the doors etc sand blasted, but I'm using an air driven DA sander on the majority of the external flat panels. What grit sandpaper would leave no marks in the metal? Is 36 grit too coarse? I bought a painting book that said to use 36 grit, so I bought some pads but it's rough as guts!

3. How long can I expect a properly done acrylic lacquer paint job to last?

["Z" UTE]

I can not comment on the suitability of your compressor for an air fed mask, but will advise against using a single compressor for both tasks. The filters on a normal compressor will never remove the dangerour vapours that you are trying to exclude. Your compressor would have to be a long way away from yout job site to even consider using the compressor air for breathing. Then you would really need vapour and oil mist filters.

As for the 36 grit paper, yes it is probably too coarse. The grade of abrasive paper depends a lot on the type of mechanical sander you use. When using a random orbital sander for example I would use 80 grit paper as the coarsest.

I had the mispleasure of having to paint a Celica which had been sanded with a disc sander and 36 grit paper. We had to lay down 5 coats of hi fill primer sanding between each coat to fill in the grooves in the metal!

An Acyrlic paint job properly applied with mutiple clear coats will last 10-15 years. The multiple clear coat gives you the ability to "colour sand" later on down the track to remove scratches and weathering. Many high end show cars were done in acrylic prior to the advent of 2pak paints.

cheers Chuck.

[love ke70]

your compressor will struggle to hold full pressure to a sander, i ran two in parallel, one little direct drive and one 3hp 15amp 3 cylinder, with the big one alone it would make about 75 psi constantly, with the pair 90-95.
makes a big difference.
i used 80 grit down to the metal and all the scratches filled in in the coat of etch primer.
allow 100 sheets and a few weekends though

[TERRA Operative]

If you are going to use an air fed respirator, you MUST (as in MUST) use a suitiable, approved filter/seperator.
If you don't, you'll be breathing oil vapour, which will coat your lungs and can potentially kill you...

[Sparkys]

Cheers for all responses! Very helpful and make my decisions easier. I will use 80 grit paper for the manual paint stripping and will use a carbon half face mask instead of an air fed mask.

Does anyone know if I have to plastic etch gel coat before applying acrylic primer surfacer?