Plating

An usual way to prevent rust, including zinc plating, nickle plating, tin plating, gold plating...etc

Baking after plating

to prevent embrittlement

Shot peening

to enhance stress relief and cleaning the surface, including Almen test and coverage report

Black phosphate / black oxide

A lower-cost way to preliminary prevent rust

ED-coating

A lower-cost colorful way to preliminary prevent rust

Powder Coating

A durable coating to prevent rust

3 ways of heat treatment

To become hard or soft

Austemper

Also called "salt-bath heat treatment". One of the ways to harden the parts. The advantage of the austempering process is that distortion is usually reduced due to the substantially higher salt bath quenching temperature.

Quenching

High temperature treatment to harden the part.

Annealing

To heat the material before forming it to avoid breaking when forming.