Ponton Mercedes-Benz 220a with fitted luggage, © Daimler AG
In the beginning I thought that the bumpers would be in such a good shape that I only had to polish them. The first inspection in probably 20 years revealed that it was not the case. The chrome was not only in a rather bad shape, the bumpers and bumperettes were also scratched and had dents. I was responsible for one or two things but obviously the usage over so many kilometers and years, partly on salty, Swedish roads, had left its marks.
First step was of course to disassembled them. Thanks to my father’s Tectyl treatment everything loosened nice and fine. However good the Tectyl had been for the bumpers, the chroming company wanted the parts cleaned from it as well as paint and rust.
I degreased and sandblasted them. The rust under the bracket holders was however too severe for my equipment so I had to take them to a sandblasting company together with the brackets.
As usual all screws, plates, washers etc was cleaned, sandblasted and plated. In some of the pictures you can see additional parts for the braking system as well as the pins etc for the spare wheel.
The brackets were powder coated. To be honest I did this by mistake and under stress, by recommendation from the sandblasting company. My opinion of powder coating is that it looks very good, is not as brittle as paint and hence can stand chipping etc better. But, if the rust gets its grip under the coating you may have problems discovering it since the rust can lurk underneath it. Well, now it is done.
The rust free bumper parts were handed in. The company was responsible for fixing dents, scratches and everything. I also told them to fix the holes for the “under-the-bumper-daylight-lights” in the side parts of the front bumpers (popular/mandatory extra equipment in Sweden during the 70 & 80ies). Unfortunately, I forgot to verify that this instruction was written down in the work statement. I discovered that when I did the check before the last part of the process, putting the chrome on. As you can see in the pictures everything has the last copper plating and are polished to perfection. I decided I didn’t want to pay for another round of work on the front bumpers, so I will have to live with these two holes. Won’t be visible, but annoying to know they are there.
The inspection revealed that one rear, side part had to be adjusted before the chroming as well as to wheel covers, one had a dent and one “dust particles” in the copper (I did the wheel covers on the same time as the bumpers, see article Wheels).
After the necessary fine tuning, the parts were chromed and the result was perfect!
Chromed Ponton bumpers and sheet metal
Painting the rear side
The chrome on the Ponton (and possibly other MB’s as well) is painted on the backside with DB158 "Weissgrau" (White-Gray). I used Spies Hecker’s 2k paint with 55% matting additive to get the correct semi-gloss finish. The DB158 was sprayed over a layer of Hagmans yellow CA-primer. During this work I made two short-cuts. We’ll see if I’ll get a problem with that in the future or not:
- During the chroming process “difficult areas” are covered with a lacquer in order not to be affected by certain parts of the process, if I remember correctly primarily the final chroming. It was explained to me exactly why this was done but unfortunately, I didn’t write it down. But it has to do with how the electric current flows in the bath and through the parts being chromed and that you want to prevent unwanted build-up, “burns” etc. In the pictures you can see where the lacquer is and then you’ll understand it better. In my case “#57002 Abdecklack-OCKER” (in Swedish “290415 Gul maskeringslack”) from Schlötter was used. It is based on ethyl acetate (ethanol in acetic acid) as solvent. The plating company said I should leave the lacquer where it was, “everyone does”. I talked to Schlötter in Sweden who said that it is “normally” taken off. I tried to peel it off, but except from some obvious loose parts it was more or less impossible and would require many, many hours of work and would probably involve heating/freezing the parts/lacquer and a lot of thinner. So, I decided to let it be where it was but carefully covered it with primer and paint. If it starts to fall off, I will take the bumpers down, clean them from all the lacquer and redo the paint.
- Chrome and paint don’t go very well together. It’s difficult to get the paint to stick. I talked to the plating guy and involved paint companies as well as some other guys. There was no one who could offer a paint/primer that they can promise will stick to shiny chrome (or the lacquer mentioned above). The best thing to do is to sand the chrome and thereafter paint but “normally” people tend to just paint the chrome and hope for the best. That is what I did. I did however also make several checks and the primer/paint seem to stick very well. If the paint starts to flake, I will take the bumpers down, clean them and redo the work.
It can also be noted that also the edges of my original chrome were painted with DB158. In the pictures the DB158 looks more glossy than it actually is (blame the photographer, sunlight and the not yet dried paint).
The reflectors in the bumperettes were taken apart and cleaned. The broken glass on one of them was repaired/glued and the cups and the spring that holds the reflectors in place were polished and then plated. The springs were painted for extra rust protection as well. The thin frames that holds the glass against the cup are made of aluminum and were only carefully polished in order not to damage the fragile chrome layer on it.
Assembly still to be made, so stay tuned!