As Shimagnolo and Grand Bois have noted, historically copper is first, then nickel, and finally chrome. But as Jim Cunningham explains in the FAQ section of the CyclArt website, new nickel formulations do not require copper to adhere to the steel and give excellent results. In fact, copper adds unnecessary weight and thickness and normally isn't used anymore unless there are recesses and pitting in the steel that need to be filled.

If I were in the market to have a bicycle frame or parts chrome plated, I'd pay the premium and have CyclArt do the work.

Jim documents the plating process here:

What is Hard Chrome Plating?

Do you triple plate (i.e. copper, then nickel, then chrome)?

What is chrome and how is it done?.