Primer Paint Options

[VoiceOff]

Sincere apologies if this is posted in the wrong section but perhaps this is a question common to many but not often voiced.

If you are working one panel at a time and want to protect the work as you go with a rattle can primer, do you go for the typical motor factor (eg Halfords) or buy Acrylic primer ? I am sure I have heard it said that Acrylic primer has a greater protective ability whereas 'normal' paint has an atmospheric absorbancy which means that your work is protected for only a short space of time - is this true or is it merely Bar Room expert opinions ?

Thanks
Ian

[John A. Ross]

Ian, any section is fine

Rattle cans are convienient but the one thing they are is expensive. Coverage wise even from 500 or 700ml cans is very poor when looking at a whole panel while buying by the litre is cheap.

Primer wise you want a nuetral coat, but before any primer the metal has to be keyed or at least etched after first defeating the brown stuff.

Everyone has their own preferences but most primers you will see in a can either have poor "etch" properties on their own or have next to no resistance to moisture. Even the factory coatings, usually black have poor resistance. UPOL Zinc Weld thru primer for attachment areas I find keys well on its own but is not a protective layer.

I have a pereference for keying material rough, nothing finer than 240 grit, wire brushes and so on are great but they tend to polish rather than key the surface.

More or less I go by the rule if it is shiny it is shoooot for adhesion. Paint adhesion on metal can be icky.

On areas that are pitted the rust needs neutrealised so I like to use a zinc phospate solution to etch the surface, it leaves it a dull grey usually but for a few days it has a zince protective coat on it so you can get in there, weld what is needed, then coat the lot in one go.

Any area I weld I like to brush in a thin layer of a good epoxy primer

Bilt Hamber 2K Epoxy

Epoxy mastic EM121 (my personal favourite)

Lesonal Sikkens 2K Epoxy

Any area I weld I like to brush in a thin layer of a good epoxy primer and i mean agressively brush in, spray is fine but I like the satisfaction of knowing its been forced in every fissure and scratch which would otherise perhaps be left with a small air pocket. It is over the top but takes no extra time.

Using some epoxy materials like the one I prefer if mixed neat can be used as a skim filler at same time, for any of the panels it is used on while they are horizontal it exhibits the same self levelling characteristics as a good finishing filler.

Once cured you can block out the epoxy and fill over it or spray an even coat on.

One thing though is you never want to be coating the material below the dew point, that is the point mositure can develop on a surface.

If you are using a base/clear the base coat does not really do much other than add colour, it is the clear coat that serves to protect from moisture or UV.



While working on a car repairing panels one at a time (which is what I do myself) rattle can etch primers will cost a fortune and cause more grief than they are worth, a decent few litres of good product from a paint suppliers will actually be cheaper.

What i do use rattle cans for is i will sometimes spray a area of top coat colour in some areas i know will be difficult to coat with the gun due to angle so they get a little extra up front.

Example a primer can might do 0.7m2 and cover poorly and be inferior to an expoxy coat, at £7 a pop for a can from retailers to cover 10m2 is almost £100

£60-70 will get you 2.5L of epoxy coat and that will do 10m2 of good coverage and seals the metal.


The epoxy coat will flash off like normal coatings but is still reacting and wont be "brick" hard until after about 10 days. Dont be tempted to blast it with heat to flash it off faster, you might end up sealing the top skin and not allowing things to flash off naturally.



I am not a painter, it is not what I do as a profession, in fact it is the polar oppossite of what i do but have prepped enough metal to jnow what sticks and what doesn't.

Dont be tempted by POR15 unless you are actually brushing it into crusty stuff itself, on good metal it has no redeeming properties to justify its use and the coating itself is not UV stable.


If you look through the pictures on JDL that car was used even outside, just in epoxy and i have actually coating some panels and left them around damp and wet areas and no issues.

John

[VoiceOff]

John,

Thank you for your input I do agree that cost wise using rattle cans is far from a cost effective option on the basis of materials, but not having a compressor, paint gun nor any space/power source, going down the spray gun route is not viable at this point in time. I have had the metal work expertly crafted for me, but time and circumstances dictate that the car has had to be stored in a pre-finished state. While the overal vehicle remains largely factory coated areas that have been repaired require either 'finishing' or at least protected for a prolonged period until futher work can be completed. It is on this basis that the rattle can option is considered.

Thank you also for the links, I will certainly look into the products suggested.

Regards

Ian

[moose549]

What about a light coat of waxoyl? warm it up and brush apply wash off with Solvent cleaner after? (i don't do body work at paint level) I have heard good things about upol raptor for protecting underside of cars.

[John A. Ross]

Mike

Raptor is the bees knees as a protective coating, did Jims engine bay in it using colour tint version and came out great. Once cured however it is as hard as advertised, brick hard.

My nephew and his mates do 4x4 mud slinging and drifting type efforts and they boath coat the cars under and outside it in and it takes a pounding, simply hose off and thats it.

Protection wise for chassis components most good epoxies when coated on thick enough will bond to the metal, so far I have dropped fuel, brake fluid, paint and all manor of other things on top and wiped most of it back off with a thinners rag and no damage.

Unlike cheaper poweder coats if the emtal is prepped and etched I find chipped poweder coat, expecially these DIY efforts will let the brown stuff leech under the coating and it falls off. the amount of powder coat we have seen fall off modern car parts gives no confidence in the coating.

Good prep on metal essential.