C2 Inside bumper finish

[Neal K.]

I just picked up my original C2 bumpers from the rechromer. They were rusty when I brought them in and I didn't think to ask how the insides would be finished. When I got them back the insides are still rugged and rusty. I asked the rechromer what the original factory inside finish was and he said that they were bare steel painted silver to retard rusting. I looked at one very old thread on this subject which advocated painted the insides with Rally wheel paint. I did not see any recent threads on the subject and am wondering if the current thinking is the same.
I would appreciate some guidance on how to finish the bumper insides so that they look factory originals.
Thanks
Neal

[Tom D.]

Re: C2 Inside bumper finish

There is a chemical mix called POR, for "Paint Over Rust". It's normal color is black, but I have seen it (or a competitor's product) in Silver. Don't expect you can find it in a spray can. I brushed it on.

[Gene M.]

Re: C2 Inside bumper finish

Neal,
For judging purposes the insides are a partial covering of chrome. Due to it being an internal shell the coverage is minimal. Plating does not respond to deep concave faces very well. The use of paint is not original. If you fog the inside with a silver paint the judges may over look it.

[Dan D.]

Re: C2 Inside bumper finish

Neal, the POR is called POR-15, and it is readily available and can be had in a variety of colors, silver is one of them. It is a very,very hard, durable paint and it the subject of varied opinions on this forum. Some people swear by it, some people hate it. It works well on rust, although they tell you to remove loose rust (makes sense) first.


It does not judge well because it goes on thick. It is also UV sensitive, but neither one of these things should be an issue on the backside of bumpers. Some of the POR products are available is rattle cans - not sure which ones. If you Google POR-15 it should come up. In my area a local auto supply store carries it. -Dan-

[Harry S.]

Re: C2 Inside bumper finish

Alternative Solution. Put two layers of Gorilla tape on all the chrome. Take the bumpers to your local media blaster and have him media blast the inside. When blasted, remove the tape and brush and clean the inside. Then apply several coats of Eastwood Diamond Clear to protect the metal. This worked well for me.

[Joe R.]

Re: C2 Inside bumper finish

One of the methods to keep the bumper from rusting and the flaking chrome off when they return from the plater is to prepare the bumper BEFORE you take it to the chromer!!!
Glass bead the inside of the bumper BEFORE and the inside may be painted silver or that ugly crap POR after plating.

When you want something done correctly PREPARATION always wins the race!

Same issue with painting a Corvette. Prepare the surface well and a monkey can paint it!

JR

[John M.]

Re: C2 Inside bumper finish

I had two sets done by Librandis and both have chrome on the inside, not pretty chrome, but chrome. It seems to me that when they prep them they'd have to clean up both sides. Anyway, I sprayed wax over the inside and the oldest are from 2002. Of course these cars don't see much nasty weather anymore but they did in a previous life.

[Michael F.]

Re: C2 Inside bumper finish

Neal,
For judging purposes the insides are a partial covering of chrome. Due to it being an internal shell the coverage is minimal. Plating does not respond to deep concave faces very well. The use of paint is not original. If you fog the inside with a silver paint the judges may over look it.

Thats how mine are finished. The chromer should have prepped the backside too. Mine have a slightly yellow partially chromed look.

[Michael F.]

Re: C2 Inside bumper finish

I have noticed replacement bumpers are very wavy on the outer surface. How smooth were the originals?

[Harry S.]

Re: C2 Inside bumper finish

Very wavy.

[Stan G.]

Re: C2 Inside bumper finish

I'm working on a 40 Ford street rod that is being repainted and the bumper guards were rusty on the insides like your bumpers . Put them in a deep pan of
Evap-O-Rust from the auto parts left them for two days washed them off and scrubbed them and they cleaned up real nice . Will spray them with a light coating of clear to keep them that way . Can you stand your bumpers up and pour this stuf inside them , do one half then the other half ? This is some great stuf you can use it over and over .

[Gene M.]

Re: C2 Inside bumper finish

I have noticed replacement bumpers are very wavy on the outer surface. How smooth were the originals?

Mike, I think you will find that the 70's vintage GM replacement parts are much worse than originals sold on mid yr Corvettes. Some of the current repops are pretty good, others real crap........

Good rechome platers can make the waves go away. The better the core the nicer the finished product.

[John H.]

Re: C2 Inside bumper finish

I have noticed replacement bumpers are very wavy on the outer surface. How smooth were the originals?

Michael -

Midyear bumpers had a welded butt joint about 4" outboard of the 90* vertical bend where the inboard and outboard sections were joined together; after welding, the weld on the show surface of that joint was metal-finished with a grinder, then with a disc sander. Between the heat of welding and grinding, that show surface was pretty wavy, some worse than others. Photo below shows a run of the outboard half, after being laser-trimmed, prior to being welded to the inboard half and metal-finished. '58-'62 bumpers were made the same way (two pieces butt-welded together). Draw die technology to form the bumper in one piece, without a welded joint, didn't appear until 1968.

MidYrTrimmed800.JPG