Chroming that lasts

[MorrisGoa]

Hi,

The 4 month long monsoon season in Goa consists of heavy rains with high relative humidity(90%+ RH). The Arabian sea winds probably add to the salinity of the air.

I had recently given bumpers, hub caps etc. for chroming, but now rust spots have appeared.

There is a new technique just introduced here called 'copper base priming'. Supposedly where a copper base is added prior to chroming. The technique used earlier didn't do this.

Surprisingly, the original Morris chrome was so excellent that the car didn't have a single rust spot for 30 years(1970 to 2000).

1. I wonder what technique Morris used?

2. Is it really worth investing in this 'copper base priming' technique?

3. Has anyone tried 'Autosol Metal Polish'? I'm thinking that this might protect the chrome.

Many thanks

[amgrave]

Originally all chroming was done using a copper base (and should still be done that way today). The metal was dipped in a solution that deposited a layer of copper on the metal and the chrome was added on top of it. The quality depended on how well the two coats were applied. Chrome without a good base will not last long as you have found out

[MorrisGoa]

Thanks amgrave.

The problem is that there is only one person who does chroming in Goa. I might have to take it to some neighbouring State.

Any idea about the effectiveness of that polish I mentioned?

[amgrave]

The polish you mention does a grand job of cleaning but will not protect the chrome, try some car wax on it after polishing.

[colin addison]

As already mentioned copper was used in the early days of electroplating as an under-layer. BUT it was then polished mechanically. This would be horrendously expensive these days, and requires great skill and the arms of an ape! Then one layer of nickel was plated, and again polished. Chrome was introduced in the '20s/30s and a double layer of nickel developed to sit under the chrome. The first layer gives the smooth surface and the second layer the corrosion resistance before applying the very thin layer of chromium. No mechanical polishing is needed. Just to add complications the chrome is actually full of microcracks (you don't see them) which have relieved the internal stress in the layer. If it didn't crack then it would curl up and not be much use. Wax will fill these cracks nicely, if you can find a clear one all the better. The geometry of the plated part is critical because the metals will plate onto sharp edges first and the deposit will get thicker on outer edges, with corresponding reduction in thickness away from edges. It is a balancing act for the plater to get sufficient metal onto the middle of parts to prevent rusting.
I hope this explains some of the problems we have with plated parts on our cars. You might have noticed there is very little (if any) chrome plating used on the outside of modern cars.
Colin

[MorrisGoa]

Thanks Colin for the comprehensive reply.

In hindsight, I should have waxed the chrome parts prior to the 4 month long humid, rust causing, monsoon season. I didn't have an inkling that the chrome would be of such poor quality. It's no use crying over spilled milk

The chrome shop claims that they just introduced this new technique which costs 30% more but supposedly fares much better during the monsoons. I'll have to get more technical details from them first, understand the difference and then decide.