Specially coated tubes are requested by GM for the hydraulic steel tubes carrying fluids for automotive, with a GM designation GE.
It is named Zinc-Aluminum Alloy-Extended Corrosion Protection by GM, and called ALGAL coating mostly in China.
It is defined as the following:
Zinc-aluminum alloy as described in GALFAN , with coating thickness 3 micrometer, i.e. 50 g/m2 per ASTM A875, followed by an approved pre-treatment process and an approved aluminum-rich epoxy coating.
The purpose of this process is still enhance the corrosion resistance of the tubes further to 1000 hr min.