POR 15 on rusty side of 48 DeSoto bumpers

[marcapra]

I finally thought it was high time to get my bumpers out of the weather and starting cleaning them up.  I cleaned the bumpers and then started the three step POR 15 method of fixing the inside bumper rust.  That area is not chromed, so it is always rusty back there.  First, I got my hand drill and a wire wheel and knocked the loose active rust off.  Then, I used Marine Clean to clean the area.  After washing the Marine Clean off, I used Metal Prep, which acts as a rust neutralizer and a pre primer.  Then I applied the POR 15 gloss black.  After two hours, I applied a second coat.  On the first bumper I did, the rear, I forgot to put masking tape over the bolt holes.  As a result, paint ran through the hole and ran on the chrome side of the bumper.  Bummer!  This paint is so tough, you can't take it off, even after just 30 minutes.  You are supposed to top coat it if it will get any sunlight.  I don't think the inside of the bumper gets much sunlight, but I could paint it will Rustoleum silver if necessary.  I even did the same process on the insides of my bumper brackets.  I'm thinking of also doing the insides of the doors and any other hidden place that might rust.  I think the chrome side of my bumpers are good enough to clean up just with using some chrome polish and steel wool 0000 fine on them.  In fact, the rear bumper was purchased 40 years NOS for about $75.  It was covered with hardened cosmolene.  I had to use paint stripper and a spatula to get it off.  I have two front bumpers and three rear bumpers, so I chose the best of each for my restoration.  I wonder what the going price is today for getting a pair of bumpers rechromed?  

Edited February 26, 2023 by marcapra (see edit history)

[Walt G]

If it were my car I would leave the black paint as it was on the inside of the bumpers, not paint it silver. the black would look more appropriate and any deep pit holes that are now free of rust would not show up as much or be noticeable as the silver would allow it to be seen.

[Rusty_OToole]

Suggest you use copper scrubbing pads and Pledge for cleaning chrome, to remove rust without scratching. The cost of chrome is something fierce if you can even get it done.

[marcapra]

Walt, I agree.  I've already decided to not paint the inside bumper silver.  Several others have told me they did this job on their cars over ten years and it stands up just fine.  I guess the only way to remove the POR 15 runs on the chrome side is to sand or file them off trying not to damage the chrome?  

[marcapra]

ARe not copper scrubbing pads pretty aggressive?  I thought I should use 0000 steel wool?  My chrome doesn't really have rust, it is pretty smooth.  see pics.  I do have a couple of POR runs because I forgot the mask the bolt holes, so I will have to use something abrasive there.  No paint stripper that I know of can weaken POR 15.  

[Walt G]

To remove the paint runs can you use a single edge razor blade? go slow and cut the layer(s) of paint off but keep the angle of the razor blade fairly flat so you aren't driving it down to the surface of the plated bumper. Once you get most of it off , Perhaps contact the POR company to see what can thin the paint that they recommend, then using a plastic wool pad ( wear gloves) dipped in the thinner and rubbing it on the paint may remove the rest of it. Plastic wool comes in assorted levels of roughness. It may take a while so have patience.

[Bloo]

I'll be the odd man out here. I'd paint it. My 36 Pontiac bumpers had a matte silver surface chrome on the back side. Methods have improved since the 30s, and unpolished areas on a bumper do not come out of the chrome tank looking like that anymore. I used flat silver paint on the inside to get a similar look. There's a million shades of silver, and I picked one that looked like the inside of the bumper. I question how long it will stay stuck, but it does look like the other bumper for now. For what it's worth, the "aluminum paint on the back side" trick is something Chevrolet was doing at the factory only a few years after that.

 

What color was the inside of the DeSoto bumper originally? If it was black I'd paint it black, if it was silver I'd paint it silver. I would use flat or matte paint to help hide flaws. One of Por-15's main weaknesses is known to be it's UV resistance. Why not shield it from UV? It's easy to do, and it can still be black if you want it to be.

 

[Rusty_OToole]

Use copper because it is soft and does not scratch. Steel wool is harder and leaves fine scratches.

[marcapra]

4 hours ago, Bloo said:

What color was the inside of the DeSoto bumper originally? If it was black I'd paint it black, if it was silver I'd paint it silver. I would use flat or matte paint to help hide flaws. One of Por-15's main weaknesses is known to be it's UV resistance. Why not shield it from UV? It's easy to do, and it can still be black if you want it to be.

 

As you may see from my pics, the inside of the DeSoto bumper was chrome for about an inch, and then rust in the middle.  I don't think the middle part had any protection from the moisture.  I don't think UV direct sunlight would find its way into the backside of a bumper.  A guy on another forum said he painted his inner bumpers with black POR 15 over 12 years ago, and it still looks the same.  I could go either way, leave it black or paint with silver.  I don't think anybody's going to see it anyway.  

[3macboys]

From experience (don't ask) I can say that brake fluid will lift the Por-15, not sure sure what it will do to the chrome though.  

[Frank DuVal]

DOT 3, 4, 5.1 brake fluid lifts most paint. That's why DOT 5 is so great on antique cars, no paint damage!👍

 

Ever try a ball of aluminum foil and water to clean rust off chrome? Works! Then follow with regular car paint polish and wax. 

[JACK M]

14 hours ago, Frank DuVal said:

Ever try a ball of aluminum foil and water to clean rust off chrome?

Better yet, Coca Cold and foil.