Cleaning up / painting old compressor

[md21722]

I have an old compressor tank that was repainted once before. It looks to me like it was shot with rattle can baby blue when another motor and pump was put on it decades ago.

When I was blowing it down after some dirty grinding work, the rattle can paint started flaking off showing a combination of the original green and red oxide type primer. The compressor and motor are also painted baby blue. Strangely the compressor pump does not seem to have an underlying coat of paint, or it came off at the same time as the blue. The pump looks like a off-market Champion like Grainger/Speedaire might sell but it has a GE motor rather than a Dayton. The tank is an old Beaird dated 1955 and is 3/16" thick all around.

From a maintenance standpoint all I would do it spray primer on any bare metal, but I am thinking it would be nice to clean up the tank and paint it all one color again. Should I try to strip all the paint and start from bare metal? Or just sand it down and shoot it with rattle can primer and paint? If sanding is suggested, what type of sander? Is this something for a 4-6" grinder with a flap disc? Or a random orbital? I have very little experience with this type of work and since I'm not particularly concerned about making a mistake, I thought it might be a nice learning experience.

Thanks

 

[RickP]

It really depends on how nice you want the paint to look when you're finished. I repainted a tank last year by just sanding the rusty spots and spraying the whole thing with primer and topcoat. Cheap rattle cans with very little prep work, and it looks it - not even close to an "automotive" finish. But it's an extra air tank that's going on a shelf in my basement, so I didn't care how it looked.

If your compressor is going to be front and center in your garage, I'd recommend sanding the whole tank with a dual action. You don't need to take it down to bare metal, but you'll get a better finish if you knock down the thickness of the 3 layers of paint already there.

 

[The Cobbler]

Perhaps you should consider a hydro test on the old tank before you decide on the quality of finish you want to do.

 

[Cyberbear]

I once acquired a large old compressor tank that was rolled 3/16" steel with hot riveted end bells, cast iron pump mounting platform and cast iron feet held to the tank by 1/2 rods, dated 1929. I had it sand blasted and repainted like a car body in brown metallic paint, using auto primer and sanded that down with an electrical orbital sander. The throw away $17.95 B&D plastic sander was cheaper than running my 3 hp compressor in order to use a jitter-bug sander. It came out great!!

 

[OccupantRJ]

I use a Dewalt dual action variable speed sander with 40-60 grit to strip and or prep equipment for painting. It has paid for itself many times over, and since it is electric it saves wear and tear on the compressor. I have two blasting cabinets for items that will fit.

 

[ms fowler]

I agree with Cobbler.
I saved an old compressor--a 3 cyl tecumseh with an old tank....so old that I couldn't read the data plate.
I worked flawlessly for several years, and then one day the entire end cap blew off at full pressure. I had the compressor under cover, but outside. Neighbor, who was a medic at Aberdeen Proving Grounds came over saying he thought a grenade had gone off. The explosion disintegrated one of those Heavy Duty plastic shelving units. Some pieces as large as a dollar bill, but most were like dime to sand sized. Also destroyed a couple of steel tool boxes and several binders of repair manuals. Could have been worse---I could have been there when it exploded.
The lesson is beware of old pressure vessels that have an unknown history.

 

[md21722]

I never get any rust out of the bottom drain, only clear water, and no rust in the lines from using it either. The data plate is clearly readable and it shows only signs of having been maintained. So I suppose that leaves the potential for metal fatigue over time unrelated to rust.