I've designed or reviewed a lot of compressed air distribution systems over the years. The pipework material question comes up on almost every new installation, and the answer isn't always the same.
The three realistic options for industrial compressed air distribution are steel (galvanised or black), copper, and aluminium (typically modular press-fit systems). Each has genuine advantages and genuine drawbacks.
Steel Pipework
Black mild steel was the standard for industrial compressed air distribution for decades. It's strong, weldable, widely available, and cheap. The downsides are significant: it corrodes internally, producing rust particles that contaminate downstream filters, foul pneumatic equipment and, in severe cases, carry through to product contact applications.
Galvanised steel is better but not immune — the zinc coating eventually breaks down, particularly at joints. In high-moisture environments without adequate drying, galvanised steel corrodes from the inside faster than many engineers expect.
For new installations, I'd only specify steel if there's a specific reason — very large bore (above DN100), very high pressure, or an environment where the lighter alternatives would be at mechanical risk.
Cost: Lowest material cost, but installation labour is higher due to welding or threading requirements.
Copper Pipework
Copper is corrosion-resistant, long-lived, and produces no contaminating particles. It's been the preferred material for compressed air in food and pharma applications for years. Properly installed compression fittings make copper easier to work with than steel.
The drawbacks: copper is expensive (and the price fluctuates significantly with commodity markets), relatively soft in larger bore sizes, and prone to fatigue cracking in high-vibration environments if not properly supported. It also requires competent installation — copper compression fittings done poorly leak more than threaded steel.
Cost: Higher material cost than steel; installation cost comparable or slightly higher.
Aluminium Modular Systems
Products like Prevost Pisco, Parker Transair, and similar systems use aluminium pipe with snap-together or press-fit connectors. They're fast to install — a significant fraction of the installation cost of equivalent copper or steel. They're also lightweight, reconfigurable, and corrosion-free.
The connectors are the area to scrutinise. Good aluminium press-fit connectors are reliable and leak-free at rated pressures. Cheap systems with poor-quality seals — and there are some in the market — leak and are difficult to repair without full connector replacement.
For workshop and light industrial applications, aluminium modular systems are hard to beat on total cost of ownership. For very large bore, high-pressure systems, or anywhere that mechanical impact damage is a realistic risk, I'd look more carefully at the alternatives.
Cost: Higher than steel on materials, but significantly cheaper total installation cost for most projects.
My Default Recommendation
For a new compressed air distribution system in a manufacturing or workshop environment, I usually specify an aluminium modular system for the main ring main and branch lines, with copper for the final drops to individual machines where flexible connections are needed. The combination gives you speed and cost on the main runs, with corrosion resistance and flexibility at the point of use.
If the application has food, pharma or strict air quality requirements, copper throughout with welded or compression fittings is the safer specification — aluminium is technically fine, but auditors sometimes query it.