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Old 05-06-2019, 07:12 PM   #1
Bus Nut
 
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Covering National School Bus Chrome

Hi,

I finally got a bus! Itís a short one. I went to a PPG dealer and told the guy what I was doing. He said that I should paint it white first before I paint it this pale green color I like. I found a jumbo sized spray booth and I will need to travel to it. Due to personal reasons I really need to get this done in one afternoon.

So a few requests for comment for those that have spray painted:

Iím interested in otherís experiences in painting over school bus yellow. Can you see the yellow through the paint?

Did you paint directly over the yellow, or did you apply some other color or primer first?

What type of paint did you use?

What color?

How many coats?

Thank You!
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Old 05-06-2019, 07:16 PM   #2
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Without knowing the chemical make up of the NSCY, I would never put new paint over old paint without a self etching primer first.
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Old 05-06-2019, 07:32 PM   #3
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I used industrial acrylic applied by an airless sprayer. I've got about 10 years on the paint so far, still looks good (much, much better than school bus yellow).

Prep was to degrease wash it, scuff up with scotch-brite pads, rinse and let dry. Water will dribble out of the rub rails for quite some time though.
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Old 05-06-2019, 07:49 PM   #4
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Quote:
Originally Posted by o1marc View Post
Without knowing the chemical make up of the NSCY, I would never put new paint over old paint without a self etching primer first.
as o1marc said, prep well, use the proper primer first - to help with coverage use a grey primer, or if you are using a white primer, tint it towards the colour you want for the finish coat - your preparation and primer are the most important part of winding up with a good job
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Old 05-06-2019, 10:18 PM   #5
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I'd say your best bet is to quickly sand it first to rough up the surface. I always figure that if the paint I'm sanding doesn't fall off while I'm sanding, then its still "sticking" to the metal underneath. A quick pass to rough up the surface doesn't take that long.

01marc is right, self-etching primer will really help - especially if you're trying to go over existing shiny/glossy paint.

All the small things I've painted always involved a coat of primer. Its great to have something sandable on there first - even just to find areas where it doesn't spray on like you expect it to (IE corners, strange round areas, etc.)

It's also a great visual gauge to how thick your color coat is coming. The first coat should start to show the final color over the primer, then the second coat the color should really fill in and look "solid."
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Old 05-07-2019, 12:02 AM   #6
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Quote:
Originally Posted by o1marc View Post
Without knowing the chemical make up of the NSCY, I would never put new paint over old paint without a self etching primer first.
Hi,

The guy at the paint shop recommended a PPG product line named Delfleet Essentials which is marketed by PPG as industrial fleet paint. I checked the tech sheet and it says it can be applied to ďProperly cleaned and sanded OEM enamels and cured finishesĒ. The guy at the shop said that I would need to sand through the clear coat before application.

I had the bus with me and when it was pointed out that I was painting over school bus yellow, thatís when he said I should paint/prime it white first. He said that itís hard to cover yellow. So, thatís why I ask.

I need to drive 100 miles each way to the paint booth and then I need to strip off parts to paint and then mask. Iíll have 2 days to prep, paint and reassemble so I want to shorten the process for that reason.

I want a quality job so maybe Iíll need to bite the bullet and do all that twice, once for primer and once for paint.

Rattle can primer?
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Old 05-07-2019, 02:39 AM   #7
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I have used PPG AUE-300 implement paint. It is a polyethylene acrilic two-part paint. I wanted to see what the minimum preparation was needed to get good adhesion, coverage and finish. I washed then used a Scotchbrite pad to rough up the surface of the old paint. I followed with acetone. I applied one coat of the paint. This was over two years ago and the paint still looks fresh. There are a couple of places where I applied masking tape and a few specs of paint were removed to show the yellow. I believe these places are where I did not really scrub it.


I also applied Rustoleum "Sandable Primer" in black (rattle can) to another section and left it for 2 months in the spring weather. I lightly sanded the primer and applied one coat of the same black paint as before. The result was very smooth. This test has been on for about 18 months with no changes in the paint job quality.


I believe that the old paint makes a decent enough primer, for my application. However, since we wanted to change the color and did not want to do *all* the preparation work (i.e. fine sanding) for the finished paint job and we still had other work to be done on The Beast before we were ready to really paint it, we applied the Rustoleum primer to the whole bus. It took approximately 35 cans for the entire bus (a 38 foot conventional) excluding the roof which was painted with white elastomeric paint. Perhaps not the least expensive way to prime a bus, but it served our purposes.
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Old 05-07-2019, 02:12 PM   #8
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I have used PPG AUE-300 implement paint. It is a polyethylene acrilic two-part paint.

Sorry, the paint is polyerethane enamel (NOT polyethylene acryllic)!
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Old 05-07-2019, 02:48 PM   #9
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Quote:
Originally Posted by o1marc View Post
Without knowing the chemical make up of the NSCY, I would never put new paint over old paint without a self etching primer first.
Hi again!

I contacted PPG Refinish technical support. They recommended epoxy primer too.

The good news for me is that if that the Delfleet Essentials primer ESU481 doesnít require sanding before shooting on the color as long as the paint is applied within 4 days of primer application. The rep that I spoke with said that I could apply the paint over the primer as soon as a couple hours after itís applied

Thank you all for your advice. Itís set me off in the right direction. Iíll post some before and after pics when Iím done.
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Old 05-07-2019, 02:59 PM   #10
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Quote:
Originally Posted by Danjo View Post
Hi again!

I contacted PPG Refinish technical support. They recommended epoxy primer too.

The good news for me is that if that the Delfleet Essentials primer ESU481 doesnít require sanding before shooting on the color as long as the paint is applied within 4 days of primer application. The rep that I spoke with said that I could apply the paint over the primer as soon as a couple hours after itís applied

Thank you all for your advice. Itís set me off in the right direction. Iíll post some before and after pics when Iím done.
depending on the quality of finish you are looking for - if the original surface is without blemish, no dust, no almost microscopic edges of old paint sticking up, it's been washed, wiped down with a tack cloth after it's in a dust free paint booth, then you can skip sanding between coats, other wise you will have a lousy finish - for assurance of a good finish I always sanded between each coat
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