Metal finishing Q&As since 1989

-----

Straightened a bent tab on newly plated steel bumper part and it peeled

January 13, 2011

I recently had a multi-part 1960 T-bird bumper assembly chrome plated with all the parts disassembled. When I went to assemble them the assembly bolt tabs on two adjoining parts were bent about 10 degrees - the same on both parts, and caused mis-alignment. (The same tabs on the opposite side were straight, and parts aligned well.) I took a rubber hammer and straightened the bent tabs. A large flake came off one of the parts: all of the tab and around the curve at the base of the tab. Of course it was the largest piece and the part of the flake that came off around the 90-degree root of the bend extended out to the visible part of the bumper. Ouch! Was I wrong to try to bend the tab (the metal is about 0.092" thick) or is the plating defective? It seems from what I've read on some of your pages that the plating should not have flaked off.



Thanks.

Don Rummell
car restorer - Midland City, Alabama, USA

---

Hi, Don. It took me a while to see the area that you were talking about, so I cropped your photo to remove extra detail, and labeled where the problem is.

This is a tough one. Plating is not supposed to peel if left alone, but it's not expected to be very flexible either. You say you only bent the tab 10 degrees with a rubber mallet to make it fit, and I don't disbelieve you; but the plater may well feel that you bent it closer to 90 degrees, or back and forth, and are expecting the impossible for thick nickel chrome plating on high strength steel. I don't believe the plater is going to do anything about this problem, but maybe other readers will offer more encouragement. Good luck.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
January 13, 2011

---

Sorry, but I have to disagree with Ted on this one. Way back when - we nickel chrome plated steel sponge mop heads which were subsequently formed around the wooden handle, a much more severe bend than what you have done, and if the plating lifted at all, we paid for the entire mop. After a bit of work on our cleaning and activation cycles, we had a failure rate of less than 0.1%. As a daily QC check, we put samples in a vice and hammered them over at a sharp 90 degree angle without peeling. This forming after plating was essentially a 100% inspection for adhesion, and we often plated lots of 10,000 parts without a single failure.

Check any junkyard and you will find severely bent bumpers with no peeling.

Your plater should have done a better job, but getting him to make it right may be a chore.

Jeffrey Holmes, CEF
Spartanburg, South Carolina
January 14, 2011

---

Almost all bumper platers will chrome strip only then polish over the old nickel, activate the old nickel and apply a new coat of nickel, then chrome plate. New nickel plating over old nickel plating does not make for the best adhesion. Certainly not as well as new nickel over bare polished steel.
However I think it would be a bit optimistic to hope you can bend a part with the heavy plating that is applied to a bumper and expect it to hold.

Frank DeGuire
- St. Louis, Missouri, USA
February 12, 2011