Steel That Doesn't Rust. POSMAC.
Zn-Mg-Al tri-alloy coated steel supplied by POSCO.5–10× the corrosion resistance of standard galvanized steel.
What Is POSMAC?
POSMAC is a zinc-magnesium-aluminum (Zn-Mg-Al) tri-alloy hot-dip coated steel developed and supplied by POSCO.
It offers 5–10× the corrosion resistance of standard hot-dip galvanized steel (GI), and its hard, formable coating stays intact through fabrication — so no post-galvanizing is required. This shortens the production cycle and reduces overall cost.
3S Co., Ltd. uses POSMAC in the Diet Cable Tray to ensure long-term durability in the harsh marine and offshore environment.
Why POSMAC?
5–10× Corrosion Resistance
Outperforms standard GI in salt-spray conditions by 5–10×. Optimized for the demanding corrosive environment of marine and offshore applications.
Forms Without Cracking
A hard, low-friction coating layer resists galling and cracking through roll-forming and bending — so the fabricated tray keeps its full coating, with no bare steel exposed.
Environmentally Responsible
Eliminating the post-galvanizing process reduces environmental load. Aligned with 3S's commitment to sustainable manufacturing.
GI vs. POSMAC
PosMAC®
Galvanized Iron
See POSMAC in Action
The Diet Cable Tray puts POSMAC's corrosion resistance to work.Non-welded, bolt-free, and up to 20% lighter.
PosMAC Grades
POSCO sells POSMAC by magnesium content.The more magnesium in the coating, the harsher the environment it can stand.
PosMAC® 1.5
1–2% MgA fine surface finish for parts that stay dry and stay seen — automotive body panels and home appliances.
PosMAC® 3.0
≈3% MgUsed by 3SSteel structures and energy installations. Over 5× the corrosion resistance of standard galvanized steel.
PosMAC® Super
5–6% MgUsed by 3SBuilt for the environments that eat steel — high salinity, high humidity, industrial air. Twice the corrosion resistance of PosMAC 3.0.
3S specifies PosMAC 3.0 or PosMAC Super depending on where the tray will live.The salt load of the deck decides the grade.