Quote:
Originally Posted by PetesPonies
That's a possibility, but why wouldn't you want to see the concerns addressed? Do you understand how and why plating is done? What anodic properties are why they are significant? If you have no interest, you don't have to visit the thread. Isn't that how threads work? Personally I would like the person who has been in the plating business to address these items. I don't know what you are expecting . .
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The anodic properties are not an issue as chrome is almost passive after plating. A metal that is anodic, will protect the substrate from corrosion by corroding in preference. This is the way cadmium and zinc protect the substrate they are plated on, and if scratched, wil still protect the substrate to a certain degree. Corrosion protection from chrome actually comes from the nickel underneath, which does not protect anodicly, but anaerobic, it blocks the atmosphere. This is why as soon as there is a scratch, the substrate will corrode. Also, if chrome is plated directly, as in hard chrome, think motorcycle forks, shock pistons etc, then the substrate will corrode due to micro cracks is the chrome deposition. These micro cracks are good for a moving part as they will hold oil, but remove the oil, or not perform regular cleaning, then corrosion will start. Modern plating is different from plating performed in the Model A era, there are a lot of additives to solutions, which make the nickel brighter, self level etc, which save a lot in labour and associated costs, but are detrimental in other areas. Bright nickel, which is used under chrome nowadays, contains oxides to perform these brightening functions, but also makes them prone to quick oxidation if not chrome plated over the top. Chrome protects the chrome by corroding on the outer layer, forming a chrome oxide layer. This will slow down any other oxidation, but not stop it. This is protects the same as anodized aluminium. Why it doesn't last long nowadays, is because it is thinner plated layer, due to costs etc.
If you need further information, read a book called 'electroplating, surface finishing fundamentals' by Frederick Lowenheim or the 'cannings electroplating handbook'