Current manufacturers of the metal parts for pens offer at least a dozen different platings. This page gives you an idea of what each type of plating has to offer and why I may or may not use it.
Gold Plating 10K and 24 K
This is the least expensive of all the platings. When exposed to constant abrasion which can be normal handling or placing the pen in your pocket the plating will wear. Manufactures may add additives or a topcoat of epoxy to make it more durable but it is almost impossible to determine what type of gold plating you are getting so for this reason I do not use it unless a particular pen is desired by the purchaser that unavailable in any other plating.
Copper plating is another soft plating that will wear relatively easily when compared to other platings. While it looks nice on some pens it is a plating I do not normally use.
This particular plating offers a unique alternative to traditional plating. If you are looking for a softer, brushed look this is your choice. Another durable plating that offers many complimentary material options. It is not as durable as some of the other finishes so I normally do not use it unless it is specifically requested.
The most durable and longest-lasting gold finish, extremely hard and durable. The plating is added in such a way that the final result is a finish that will virtually never show wear and always retain the glowing gold finish. The gold finish of choice for my pens.
18 Karat Swiss Rose Gold
A unique plating that combines copper and gold which is deposited in a very thick layer producing an attractive and durable pen part. The copper in the alloy may cause the finish to tarnish but if this happens the original luster can be brought back by lightly buffing the surface.
A titanium oxide plating that results in a very hard and durable surface that will last for many years. One of my personal favourites.
Platinum produces a very durable and hard plating that can be expected to last for many years under normal use.
Parts that are plated with sterling silver receive a restaurant grade 20 micron plating which is very durable to ensure that the beauty lasts for many years.
Rhodium is a member of the platinum precious metal family but has unmatched brilliance and durability. Many manufacturers in the jewelry industry use rhodium to plate their fine jewelry pieces. Some of the world's premier pen manufacturers even use rhodium to plate their very finest pens. Almost all of the current pen manufacturers guarantee their rhodium finishes for life.
A durable plating that under normal use should hold up for many years.
Also a very durable finish that offers an alternative to the traditional chrome plating. Contrasts nicely with lighter coloured woods.