Question Painting Raw Aluminum + Reflective

[TXFB.INS]

afternoon from the oven roaster.

got a customer who is a road side service & repair provider.
They have built a custom truck bed out of aluminum, and wants to paint it before we apply graphics.

They have asked what type of paint and prep is needed for the painting to improve adhesive of graphics
since I know only enough to tell them about out gassing and waiting before graphics.
my question is

• prepping raw aluminum?
• type of primer?
• type of paint? ( they are painting black)
• Is there a finish that is better for reflective adhesive?
• How long for out gassing?
• Does the VOC like wall paint play a factor?

Much appreciation

 

[Gino]

You might wanna let the Auto Body Shop doing the work make those suggestions. A good oven baked finish would be best for any graphics.

 

[TXFB.INS]

You might wanna let the Auto Body Shop doing the work make those suggestions. A good oven baked finish would be best for any graphics.

There is no auto body shop involved.
end customer built their own truck bed and will be doing the painting. I also highly doubt they have a paint / cook booth

 

[Gino]

Well then, I'd stay clear of making suggestions, regardless of what you hear and/or read here. There are only 2 or 3 people on here qualified to answer you and hopefully they will. All others will be personal emotional answers. Have them get it from the horses mouth of some body shop in your area.

 

[unclebun]

They have to use an aluminum primer (self etching) first. Then any regular automotive paint will be fine, and you follow normal outgassing time (30 days is usually quoted). On the other hand, we used to roll on bulletin enamel and dry a day or two and then apply vinyl lettering, and it seemed to stick better than if you waited longer.

On the other hand, they might not be auto body people, and wanting to use household-type paints. You can go to the hardware store and buy rattle cans of self etching primer, and then use gloss black.

On the other hand, regular engineer grade reflective sticks perfectly well to raw aluminum. That's how traffic signs are made.

 

[TXFB.INS]

They have to use an aluminum primer (self etching) first. Then any regular automotive paint will be fine, and you follow normal outgassing time (30 days is usually quoted). On the other hand, we used to roll on bulletin enamel and dry a day or two and then apply vinyl lettering, and it seemed to stick better than if you waited longer.

On the other hand, they might not be auto body people, and wanting to use household-type paints. You can go to the hardware store and buy rattle cans of self etching primer, and then use gloss black.

On the other hand, regular engineer grade reflective sticks perfectly well to raw aluminum. That's how traffic signs are made.

Much appreciation.
I suggested sticking to the raw material, we have done that plenty of times all still is good.
they want it painted black, do not want the "aluminum" seen.

will suggest the paint / body shop first and go from there

 

[equippaint]

Best way is to etch and alodine but that process is going to the wayside. Degrease it, then use a red 3m pad with white vinegar and scrub the entire thing (that's the etch). Clean it all off well, then alodine, then epoxy, then use a 2k polyurethane.
Another way is to etch same way, then use a 2 part etching primer, then epoxy, then 2k polyurethane.
Another option: This is what we are doing now per PPG after they stopped the etching primers. Sand with 80, epoxy primer (make sure its DTM rated for aluminum like Axalta), 2k polyurethane topcoat. You have to make sure that every bit is sanded or it will peel off. You can also etch instead of sand.
We also will sandblast aluminum for the profile but you can not use a self etching primer over it, it will bridge the profile and fail. This works well but can be a bit aggressive and leave a rougher finish. Do not use any media with steel in it or it can embed into the aluminum and cause pinholes from galvanic corrosion.
The stair truck is sanded and epoxy
Tow truck was sandblasted and epoxy
Reefer trailer was etched with vinegar, self etch primer, epoxy
all have 2k polyurethane single stage top coats

 

[GB2]

The prep and paint won't improve adhesive of graphics, the vinyl will stick just fine to almost any paint they would use, the issue is having the paint adhere properly to the aluminum, which is a challenge for a professional to get it right. Apparently, Equippaint has the right idea above but I would definitely suggest they seek out a professional in the field of truck painting, unless that is something you want to get into.

 

[signbrad]

Our process for raw aluminum:
Clean with water. Then solvent wash. Sand thoroughly with a DA sander. We use 150 grit paper. Then solvent wash again. Tack wipe. Spray acid wash primer. (Matthews is 74 760SP PT Filler). Add the "activator" to the PT Filler just before spraying. The activator is the acid component. The primer dries quickly. Then topcoat with any Matthews Acrylic Polyurethane color, mixing in the catalyst and reducer according to specs, and adding Accelerator 287 437SP in addition to the catalyst and reducer. Spray tip is 1.4mm on an HVLP gun. Adhere to specs for all Matthews products. Especially the catalyst and accelerator amounts. Never add extra catalyst on the assumption it will dry quicker. It will interfere with curing. Vinyl can be applied next day with no problems if the accelerator is used. No need to wait. Without accelerator Matthews recommends a 72-hour wait before vinyl.

Body shops use similar products. If an acid wash primer is not available, an epoxy primer is suitable. Then topcoat with a polyurethane enamel. Stay in the same brand family for primer and finish coat. A catalyzed polyurethane is the most durable automotive finish these days.

Some random thoughts on refinishing:
If aluminum is anodized, the anodized layer must be removed completely by sanding before painting. It can prevent good adhesion of Matthews paints.

New factory-painted aluminum should not be primed. It should be sanded thoroughly, however, before topcoating. More and more, prepainted aluminum is finished with PVDF coatings. These are flouropolymers rather than polyurethanes. They get very hard and can resist a topcoat, so must be thoroughly sanded prior to repainting. A light scuffing with a Scotchbrite is not enough. Kill the gloss using 400 grit paper. Not all prepainted aluminum is finished with PVDF, but it is safer to assume that it is.

Old painted panels should never be primed with PT Filler, even if you have "sand-thrus" when prepping. Always use epoxy primer for this. PT Filler is not made to be "sticky." It is made to etch into metal. So it does not perform well on old painted surfaces. It is made for raw aluminum and steel only. Epoxy will adhere better on old paint and will yield a nice uniform base for the topcoat.

Brad in Kansas City

 

[rjssigns]

Lots of DTM(direct to metal) products available.
I like epoxy priimers and would start with a product like this: https://www.sherwin-automotive.com/about-us/press-releases/new-direct-to-metal-primer

 

[signbrad]

Lots of DTM(direct to metal) products available.
I like epoxy priimers and would start with a product like this: https://www.sherwin-automotive.com/about-us/press-releases/new-direct-to-metal-primer

I like epoxy primers, too. Actually, I prefer Matthews epoxy primer over Matthews PT Filler acid wash primer for priming aluminum and steel. But bossman insists on the much faster drying PT Filler. The Matthews epoxy primer comes in white and black. I usually order a gallon of both. I often make my own gray that way, since the white doesn't always want to kill a previous color. The Matthews epoxy primer also has a rust inhibitor, which their PT Filler does not have.

The SW E2A400 epoxy primer you reference looks like a good product. I have always had a great deal of confidence in Sherwin Williams products.

Brad

 

[equippaint]

I like epoxy primers, too. Actually, I prefer Matthews epoxy primer over Matthews PT Filler acid wash primer for priming aluminum and steel. But bossman insists on the much faster drying PT Filler. The Matthews epoxy primer comes in white and black. I usually order a gallon of both. I often make my own gray that way, since the white doesn't always want to kill a previous color. The Matthews epoxy primer also has a rust inhibitor, which their PT Filler does not have.

The SW E2A400 epoxy primer you reference looks like a good product. I have always had a great deal of confidence in Sherwin Williams products.

Brad

The acid should kill the rust in theory but epoxy is superior and has essentially replaced all other types of primers. There is really no need for etch primer anymore. We use a few different epoxies depending on what it is. Axalta for new blasted steel and aluminum because it goes on easy and leaves a nice smooth surface for a direct topcoat. We also use a high build marine epoxy that we use over things that have been blasted but had a lot of rust. Its harder to get it to lay flat, by nature its peely so its limited to being used on industrial type applications. Many industrial jobs spec SW macropoxy 646 so we also use that quite a bit, it dries too slow for me though. I'm not a fan of gray primer either, it's too hard to see coverage on bare metal. Same deal with the topcoat, unless its a yellow, Id prefer red to be able to see how much topcoat is going on. Many marine jobs will spec alternating color primers i.e. 1 coat red, 1 coat white and whatever topcoat for this reason. I think painting is more technical than people realize.

 

[visual800]

we paint aluminum, scuff, clean with wax grease remover, prime with 2 part epoxy primer and then BC/CC or signle stage.......to be honest with you if THEY are going to paint it explain what you are not liable for