Methods vary depending on several factors:
Type of base metal that the chrome is currently appplied to (steel, iron, aluminum, etc)?
Size of the piece to be stripped (e.g. a front bumper vs. a door handle)
Is the intention to re-chrome the piece (after it has been de-chromed)
Basically there are 3 viable methods:
1. Mechanically - using sandblasting/wire wheel
2. Chemically - immersion in a strong muriatic bath
3. Electrolysis - similar to the rust removal method - as discussed in this thread:
http://www.gmsquarebody.com/forum/showthread.php?t=372&highlight=electrolysis
But the electrolyte solution used in chrome removal is an acid (muriatic/hydrochloric) as opposed to the alkaline bath (caustic soda/Drano/antler cleaner) that is used for rust removal.
Here is a quick overview of the electrolysis method for chrome removal:
The proceedure is very much the same as removing rust but with different chemical. First, degrease completely and scrub thoroughly with detergent. Mix 1 cup of Muriatic acid with 3 gallons of water in a plastic bucket. NOTE; ALWAYS ADD ACID TO WATER. NEVER WATER TO ACID !!! (It WILL explode) Hang two or three copper wires (#12 or larger) around sides of bucket. Connect these to ground of battery charger. Hang item to be dechromed in fluid with positive lead connected. Be sure part doesn"t touch ground wires. Within a few seconds or minutes, depending on thickness of chrome, it should come clean. More or less time as required. When finnished, wash parts in mild soda water solution to nutralize acid. (Do this right way to prevent rust)
BTW - it would be prudent to do further research on this procedure yourself before attempting. For all you know, I could be a misinformed nutcase who gives out dangerous advice.
Before trying anything else, see how this simple/safe method works - let the piece soak in a bath of plain old brake fluid (or paint it on if its a big part that is still on the truck).
Give it some time to work. Then, starting at a spot where the chrome has chipped off, scrub hard with a green Scotchbrite pad.