I have a smattering of parts that need to be re chromed. A few derailleurs and some hubs. What d I need to do before having these pieces chromed. I already pulled the cogs off of the der. and I was wiondering if the chroming process would freeze theese pieces permanently?

I have had some gun parts plated before, so I will pass on what I learned from that.
The plating is gonna add material to your parts so you have to take that into consideration. If the parts were plated before, then I am sure that this was figured into the tollerances. All parts will have to be taken apart so you are plating single objects, not assemblies. You will have to prepare the parts, this means polishing them so there are no visible surface defects. Any pits or scratches that you can see will be visible after the plating. As you are polishing the parts, wear cotton gloves (the inexpensive brown cloth gloves work really great!) so you don't leave fingerprints that might show up in the plating! Other than that, nothing to it!! Any other questions, you should probabely check with the plating shop to see if they have any special requirements. good luck

Plating is pretty expensive, try and find some other people who also need some stuff plated, group up and reduce the cost. Try vintage hotrodders, they get a lot of stuff chromed.

Try a wheel chromer, or a wheel specialist. They usually deal in chroming of basically anything, and can give you details on what you will need to do in preparation for the chroming of your bits and pieces.

expensive? i had my brake screws and nuts plus a number of small parts professionally chromed..

I paid the shop 20 pesos.. That's about 35cents US.

Price varies from country to country, and also on the professionalism of the job