The typical steel used in many fixed gear bikes, 4130, corresponds to the steel used in guns.

Makers of very expensive guns in the late 1800's and early 1900's would create a corrosion-resistant patina they called "browning."

The process involved keeping disassembled gun parts in a cool, humid room, and wiping them down daily with a damp, slighty-oiled rag.

When treated this way, conscientiously and consistently, steel will turn golden, brown, or grey; and, will resist further corrosion, in the absence of salt.

Nickel and aluminum form a protective oxide layer in the presence of oxygen, and will turn a dull silver color.

I like the look of nickel.

One of the instructors at the United Bicycle Institute (Ashland, Oregon) had his or her lugged-steel fixed-gear frame plated with pure nickel and it looks beautiful; much nicer and more under-stated than chrome (not as hard as chrome, though, and more subject to wear and tear).