Materials
Alloys, densities and finishes
Material choice usually decides the price of a perforated sheet more than the pattern does. This is what we run, what each is for, and when the cheaper grade is a false economy.
Stainless steel
Stainless Steel 304
General filtration, architectural, food contact
7,930
kg/m³
The default stainless. Good all-round corrosion resistance at sensible cost.
- Corrosion
- Very good
- Magnetic
- No
Stainless Steel 316 / 316L
Chlorides, amine service, marine, pharmaceutical
8,000
kg/m³
Molybdenum addition resists pitting where 304 would fail. The grade for coastal Mumbai and chloride streams.
- Corrosion
- Excellent
- Magnetic
- No
Carbon steel
Mild Steel
Machine guards, structural screens, powder-coated panels
7,850
kg/m³
Lowest cost. Must be painted, powder-coated or galvanised for any outdoor use.
- Corrosion
- Needs coating
- Magnetic
- Yes
Galvanised Iron
Fencing, cable trays, outdoor guards
7,850
kg/m³
Zinc-coated mild steel. Cut edges stay exposed unless re-galvanised after perforation.
- Corrosion
- Good
- Magnetic
- Yes
Non-ferrous
Aluminium
Facades, ceiling mesh, sunshades, signage
2,700
kg/m³
About a third the weight of steel — the reason it dominates facade work. Anodises well.
- Corrosion
- Very good
- Magnetic
- No
Copper
Decorative screens, filtration, electrical
8,960
kg/m³
Weathers to a patina. Soft, so thin webs tear more readily than in steel.
- Corrosion
- Very good
- Magnetic
- No
Brass
Decorative panels, instrument screens, grilles
8,500
kg/m³
Chosen for appearance more often than performance. Polishes to a bright finish.
- Corrosion
- Good
- Magnetic
- No
Specialty alloys
Monel 400
Seawater, hydrofluoric acid, demister pads in marine service
8,800
kg/m³
Nickel-copper alloy. Specified where even 316L is not enough — typically seawater and acid duty.
- Corrosion
- Excellent
- Magnetic
- No
Titanium
Aggressive chemical service, heat exchangers
4,510
kg/m³
Outstanding corrosion resistance at low weight. Specialist tooling and longer lead time.
- Corrosion
- Excellent
- Magnetic
- No
Finishes
Applied after perforation, not before
Coating a sheet and then punching it leaves bare cut edges — which is exactly where corrosion starts. Finishing follows perforation in every case but mill finish.
Mill finish
As-rolled. The default, and the cheapest.
Powder coating
Any RAL shade. The usual choice for mild steel and aluminium facades.
Anodising
Aluminium only. Harder and more durable than paint; natural, bronze and black.
Electro plating
Decorative and corrosion-resistant layer on steel and brass.
Hot dip galvanising
Heavy zinc coat for outdoor steel. Applied after perforation.
Polishing
Mirror or satin on stainless and brass, for visible architectural work.
Choosing a material
- Which stainless grade should I specify?
- 304 unless there are chlorides. 316 or 316L adds molybdenum, which resists the pitting that destroys 304 in salt air, seawater and amine service. In coastal Mumbai, exterior stainless is usually worth specifying as 316.
- Why is aluminium used for facades rather than steel?
- Weight. At 2,700 kg/m³ aluminium is roughly a third the density of steel, so the supporting structure can be lighter and cheaper. It also anodises, giving a finish integral to the metal rather than painted on top.
- How do I convert open area into sheet weight?
- Take the solid weight — thickness in metres × density × area — then multiply by (1 − open area). A 2 mm SS 304 sheet at 35% open area weighs 0.002 × 7930 × 0.65 ≈ 10.3 kg/m². Our pattern designer does this live.
- Is the finish applied before or after perforation?
- After, in almost every case. Perforating a coated sheet leaves bare cut edges, which is exactly where corrosion starts. Powder coating, galvanising and anodising are all applied once the holes are in.