AN EXPLANATION OF PLATING USED ON PENS
Since plating is such an important part of writing instrument kits I would like to offer a brief explanation of pen plating in general.

GOLD PLATING. Gold plating is ultimately not durable when exposed to abrasion. Gold plating can be made more durable depending on the method used to plate, additives to the gold, and techniques employed. No matter what, is done all gold plating will wear off over time when abraded. This is simply a fact of physics. Plating other than gold can be very durable. The following is an explanation of the various plating used.

GOLD. 24K "upgrade gold". Upgrade means that the parts are plated using the rack method and that small amounts of cobalt or palladium are added to the plating chemicals. This enhances the durability of the gold plating.

TITANIUM GOLD. This method produces extremely durable and the most durable gold plating. The process used is called PVD (particle vapour deposition). Titanium nitride matched to the colour of gold is molecularly bonded to the part and then 24K gold is bonded on to the part to achieve a colour match to other gold parts. The parts are again re-plated after this. The final result is that the parts will virtually never show wear.

CHROME. This is an extremely durable plating. Under normal use this plating should hold up for many years

PLATINUM. This is very durable hard plating, it should be expected to hold up under normal careful use for many years.

BLACK TITANIUM. This is titanium oxide molecularly bonded (PVD). This plating is unbelievably hard and durable. It will last for many years.

BLACK CHROME. Black chrome is an extremely durable, rich, and bright black plating.

COPPER. The bright and satin copper plating's have a proprietary coating over the copper. This coating provides superior durability and tarnish resistance.

RHODIUM: is possibly natures most brilliant and durable precious metal and the rarest of all non-radioactive metals on Earth. The world's premier pen manufacturers use it to plate their very finest work. Rhodium can sell for as much as £700 per ounce and was discovered in 1803 by W.H. Wollaston. The name is derived from the Greek ‘rhodon’, meaning rose

Information sourced from various professional pen making resources across the web