What spec should be on a print for chrome plating?

Can you chrome plate aluminum? Why would you when you can polish it to look as good as chrome? I used to work for Chicago Pneumatic who makes air impact wrenches and such, and they just polished the aluminum housing, and it looked great.

Customer is rejecting an order we grained and sent off for Chrome Plating.

Who wants grainy Crome?

But according to my plater they have stated a call out should be on print.

Polish #400 prior to plating?

Polish #400 prior to plating?

This too course and could cause a grainy finish, suggest specify polish surface condition/finish quality in microns instead.

13 microns is slightly larger than 1/100th of a millimeter.

A good brilliant nickle finish could be 10 microns.

Polish the aluminum before plating and polish the nickle before chroming.

My recollection is that the differential thermal expansion will damage the chromium.

As "bob c" asserted the best method to develop a great shine is copper/nickle/chrome.

However the "cheep" less expensive method is aluminum/nickel/chrome.

caveat emptor!

Chrome plating isn't just for looks.

There is also a hard chrome plating that is polished for a smooth durable surface that is going to be subjected to a lot of wear from a chain riding over it.

The chrome plating is usually a three stage process, copper, nickle followed by chrome. But it is all for nothing if the material being plated is not polished to the brilliance your customer is requiring. "Polished to a mirror like brilliance" should get the job done.

Cu/Ni/Cr as mentioned earlier is correct but you should note that this finish tends to break down eventually. A product I used to be involved with would have this finish if requested but it always started to blister after a couple of years even in benign indoor conditions.

The customer should have specified the plating requirements. Leaving anything open to interpretation is a bad practice. If the customer doesn't know the spec's that he requires, it makes it very difficult for you to produce a product to his satisfaction.

As one of the other posts mentioned, there are different types of Chrome Plate. If the customer requires decorative chrome, inspection criteria can be very subjective. You need to find exactly what he wants. He should give you either specifications or samples. You then need to contact a plating company (and possibly a polishing company) to see if the requirements are realistic.

Document everything. Good Luck!