DKP, galvanised, stainless. Gauge to millimetre, weight to cost, and which grade survives a Jeddah salt-spray test. The metal you pick at design freezes the cost, the corrosion life, and how the workshop hates you.
14-gauge sheet is 2.0 mm. 16-gauge is 1.5 mm. 20-gauge is 0.9 mm. Higher gauge number = thinner sheet. Same gauge in steel and aluminium are not the same stiffness.
Drawing-quality cold-rolled steel is the workshop standard for painted enclosures. Bare DKP rusts in weeks. Only spec it indoors under a real paint system.
HDG Z275 carries 275 g/m² of zinc, ~20 microns each side. In Saudi inland environments it lasts 20+ years before red rust. Coastal halves it.
Jeddah and Dammam coastline: 304 tea-stains in a year. 316 with 2% molybdenum survives. Within 200 m of saltwater or direct spray, spec 316 or nothing.
Common gauges NLC uses for luminaire bodies, control panels, and outdoor enclosures.
| Gauge (SWG) | Thickness · Weight | Typical use |
|---|---|---|
| 22-gauge | 0.7 mm · 5.5 kg/m² | Light luminaire trim, covers |
| 20-gauge | 0.9 mm · 7.1 kg/m² | Indoor lighting bodies |
| 18-gauge | 1.2 mm · 9.4 kg/m² | DBs, indoor electrical enclosures |
| 16-gauge | 1.5 mm · 11.8 kg/m² | MDB doors, outdoor luminaires |
| 14-gauge | 2.0 mm · 15.7 kg/m² | MV cubicles, outdoor MDB |
| 12-gauge | 2.7 mm · 21.2 kg/m² | Switchgear frames, structural |
| 10-gauge | 3.4 mm · 26.8 kg/m² | Heavy industrial enclosures |
Once the metal is cut, you live with it. Get the choice right at spec.
Doubling thickness gives 8× stiffness, not 2×. A panel door at 1.2 mm flexes when you press it. Same door at 2.0 mm feels solid. The customer reads "solid" as "quality" before they read the spec sheet.
To match a 1.5 mm steel panel's stiffness, you need ~2.4 mm aluminium. The weight savings shrink. The real win is corrosion, not weight, aluminium oxide is the paint that paints itself.
Powder coat is a 60-micron polymer. Scratch it, and bare steel under it rusts. HDG underneath gives a sacrificial zinc layer that protects the scratch. Coastal Saudi specs should always be HDG + powder.
"1.5 mm sheet steel" is a useless line in a BOQ. It can be DKP, S235JR structural, electro-galvanised, or hot-dipped. Cost varies 3×, corrosion life varies 30×. Write the grade.
Tea-staining (light surface rust on 304) shows up fastest on brushed finishes because the grooves trap chlorides. If aesthetic matters at the coast, spec 316 brushed or 304 with a polished No.4 finish that sheds water.
Our sheet-metal shop runs DKP, HDG, 304, and 316 lines side by side. CNC punch, laser, brake, and weld in one facility, with phosphate pre-treat and a 16-zone powder oven downstream.
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