CHROME: Chrome is a very familiar metal plating. Chrome is an excellent choice for a moderately priced plating that is quite durable and wears well. Chrome has a brilliant shine and compliments  any pen.

GOLD-24k: This is gold in it elemental form, and though the plating may be somewhat thick and well done, will eventually wear showing the base metal underneath. The base metal is often a brass alloy and the wearing of the gold to expose the brass base is called brassing.

GOLD-22k and 10k: This plating is an alloy of gold and other metals. Although much more durable than 24k, even this gold will eventually show wear and brassing.

Many gold plated pen parts are covered with an epoxy coating which helps to make the gold plating more durable and wearable. But remember, thses gold platings will wear away with time.

TITANIUM GOLD: Titanium plating produces one of the the most durable finishes...In fact, it may well be the hardest of all metal finishes on pens.  The process uses what is called PVD (particle vapor deposition). Titanium gold is a cost effective alternative to real gold. Titanium  and zirconium nitride is matched to the color of real gold and is molecularly bonded to the pen parts, 24k gold is bonded on the parts to achieve a color match to  gold and parts are again re-plated after this step.  The final result is a lustrous bright gold finish that will virtually never show wear. 

BLACK TITANIUM: A very durable finish. The black titanium finish is produced very similarly to the gold titanium process above. But instead of a gold layer, a black later is bonded between the titanium and zirconium nitride layers. Black titanium can take on several different looks depending how light is reflected. The color can be various shades of black, grey, gunmetal or chorme.

PLATINUM AND RHODIUM:  These two metals are closely related and are chrome or silver in color. They are both very durable and will give many many years of trouble free service. Platinum and rhodium are an elelgant and rich looking finish for pens.

A FINAL WORD ON PLATING:  There is no way to give a quantitative answer as to how long these platings will last. Wearability will be largely determined by the usage, the environment where the pen is used, the body chemistry of the owner, and the care with which the pen is given. Generally, with proper care, any of the platings will give years of service, the titanium, platinum and rhodium, decades.