Painting bus top Roll On Primer?

[Rick59-4104]

 The paint on my 4104 looks good except for the curved roof section above the windows, there are several places where the paint and primer have come off down to the aluminum. The aluminum on the roof is not anodized, and looks like it was never sanded to give the primer a good surface to "bite" into.

I am going to do the prep work myself and have a friend spray probably a PPG single stage white paint. I am using 3M paint stripping disks, wire cups on an angle grinder, and then going over the surface with a DA with 180 grit and using stripper around the rivets. Not trying to get all the old paint and primer off but smoothing and blending the surface into the bare areas.

Any one have experience with the roll on primers? My thinking is that since I am doing the prep work outside if I roll the primer on I will just have to mask once when we move the bus into a borrowed shop to spray the finish paint. Plans are for a white top with a blue border and then to letter Highway Traveler like the original 04's were lettered.
Any one see anything wrong with the plan or have any advice???

Thanks
Rick

[wal1809]

If you can see it from the ground I would not roll the primer onto the bus.  I say this because your going to see the blemishes right through the color coats.  If it is in an area where you can't see, like on top, then I would use the elastimer coating to help insulate and cover the roof.  Elastimer is about $75 for a 5 gallon bucket and you can roll it on.  I did 3 coats and it is over a 1/4 inch thick.

If your going to be able to see it then I would spray the primer, sand again and spray your color coats.

[Highway Yacht]

If you can see it from the ground I would not roll the primer onto the bus.  I say this because your going to see the blemishes right through the color coats.  If it is in an area where you can't see, like on top, then I would use the elastimer coating to help insulate and cover the roof.  Elastimer is about $75 for a 5 gallon bucket and you can roll it on.  I did 3 coats and it is over a 1/4 inch thick.

If your going to be able to see it then I would spray the primer, sand again and spray your color coats.

Did you get all 3 coats from the one 5 gallon pail??

Jimmy

[wal1809]

3 coats with about a gallon left over.

[jjrbus]

Down the center of the top you do not want a silky smooth surface.  Not a place to wax.

Maybe even spread a little sand in the paint..   JIm

[junkman42]

On bare aluminum You are going to have to apply alodine or perhaps one of the self etching primers intended for aluminum!  Bare aluminum will shed paint everytime if not properly prepared!  Look up Aircraft Spruce and Speciality and You will find the proper products.  John L

[Oonrahnjay]

3 coats with about a gallon left over.

What was the brand name of the coating you used, please?   Thanks,  BH NC USA

[Uglydog56]

I thought you wanted to keep the roof smooth so it wouldn't collect dirt in the texture and reduce the thermal reflective properties of your roof treatment.  i do understand wanting to make it able to be walked on without slipping and falling.  Am I out to lunch here?  Learning here.

[gus]

You can also prime the bare Al with spray can zinc chromate if you can find it.

If you use it just apply a very thin coat, thick coats peel and don't prime as well.

[Rick59-4104]

 I have settled on 80 grit 3M paper on a DA sander, (stay away from the rivets) changing over to 180 grit when I get close to the metal. The bus has red and yellow primer under a couple of coats of paint I am thinking this is the original primer, will talk with my paint guy and see if this needs to completely come off or if I can primer over it in places. 

On a side note I was on my way to a friends today to borrow a couple of sets of scaffolding for the bus painting project, drove by an auction in process, started to stop, drove on, changed my mind and went back. I started toward the crowd, had my wife go get a bid number the first item selling as I walked up was 2 sets of really nice scaffolding/braces made from 3/16" square tubing. Got the 2 sets for $22.50. Funny how some times things just work out

Thanks for all the advice.


Rick

[babell2]

I am using 3M paint stripping disks, wire cups on an angle grinder, and then going over the surface with a DA with 180 grit and using stripper around the rivets. Not trying to get all the old paint and primer off but smoothing and blending the surface into the bare areas.

Any one see anything wrong with the plan or have any advice???

The only thing that throws up a red flag to me is the wire cup on aluminium. Steel wire brushes on aluminum can leave fragments of steel embedded in the aluminium leading to corrosion. The 3M stripping disks are synthetic and the sand paper is usually aluminum oxide so not an issue. If you really want it clean use a aircraft tal strip product around the rivets and plan a blend line away from a rivet line.
  A Good self etching primer will give you that good bond to the metal or has been mentioned before alodine prep.

Brice

[eddiepotts]

You will have no problem with rolling on the primer. Get the right primer for aluminum and have at it. In auto paint and body class that's all we did. What ever work you did you had to primer it before the end of the night. At Home depot they have a small plastic foam roller that we would just throw the foam away.you will have to wet sand any primer for a perfect finish. Even if you sprayed it.

[rgrauto]

Rick  I tried the roof coating and and found that  in two or three yrs it started chalking and streaking the paint and windows.  I painted the roof on our bus Sept 2010 and I used a self etching primer on the bare metal and regular primer on top to be able to sand to a smooth finish. You can do primer work outside because it dries fast and with very little masking (24 inch paper)  then when you sand smooth,re-primer any bare spots,re-sand and you are ready to paint.  If you are going to paint stripes over your new paint,use the correct masking tape and the appropriate time you can safely tape on the new paint. If you paint the stripes soon enough you don't need to sand to make them bond,  This is the way I did mine using acrylic-enamel paint because price,easy to use (for me) and no clear to peel.  It's been about a year and the paint looks just like it did when I painted it.    Now I'm not a auto body repair man,not a painter but I've always done my own stuff and saved/made money doing it and you can too with a little research.  I hope this helps you a little, but you do it your way, Glen Rice