Solar strut channel is usually supplied in two coatings: hot-dip galvanized (HDG) and zinc-aluminum-magnesium (ZAM). Both protect the steel, but they are different processes with different costs and service lives. Here is how they compare.
Coating process
Hot-dip galvanizing immerses the steel in molten zinc, leaving a pure zinc coating on the surface. ZAM coating is a newer alloy process: on top of the zinc, it adds aluminum and magnesium elements to the coating, forming a zinc-aluminum-magnesium alloy layer instead of plain zinc.
Corrosion resistance
The alloy layer is what changes everything. ZAM-coated channel resists corrosion substantially better than plain hot-dip galvanizing, which means a longer outdoor service life for racking that stands in the field for 25 years or more. This is why ZAM is becoming the default specification for new solar racking projects.
Weldability
Welding quality directly affects the stability of the finished racking. Plain hot-dip galvanized steel is prone to weld-zone problems — porosity and corrosion at the weld — because the zinc layer burns and breaks down under the welding arc. ZAM’s alloy coating behaves better under welding, which makes the assembly line of a racking factory simpler and faster.
Cost
Because of the newer alloy process and its supply chain, ZAM-coated coil is generally priced below equivalent hot-dip galvanized coil on a per-ton basis — which is exactly why the economics of switching work in favour of ZAM. Coil prices vary by mill and market, so always compare current quotations for your region.
| Coating | HDG: pure zinc layer | ZAM: zinc-aluminum-magnesium alloy layer |
|---|---|
| Corrosion resistance | Good | Substantially better — preferred for 25-year outdoor service |
| Weldability | Weld zone prone to porosity and corrosion | Better alloy behaviour under welding |
| Typical use | General steel structures | Solar racking, telecom towers, long-life outdoor structures |
| Relative cost | Baseline | Generally lower per ton (mill-dependent) |
Which should you choose?
If corrosion life and weldability are priorities for your channel product — and in solar racking they usually are — ZAM is the specification to plan around. If your market still specifies HDG for price or availability reasons, a line built for galvanized coil runs both without problems.
Before you specify the coating for your line, send us your target profile, coil type and market — we will confirm the compatible punch, forming and cutting configuration. View our solar strut channel roll forming machines.
