Comparing RF Shielding Materials: Copper vs. Galvanized Steel vs. Aluminum

The material selection for an RF shielded room affects shielding performance, long-term reliability, construction cost, and the frequency range over which the shield is effective. Copper, galvanized steel, and aluminum each have distinct performance profiles—and each has applications where it's the clear right choice and others where it's the wrong one.

This guide gives you the technical comparison you need to make the right material specification before your RFP is issued.

The Physics of RF Shielding Materials: What Actually Matters

RF shielding effectiveness depends on a material's electrical conductivity, magnetic permeability, and thickness—not just one property in isolation. At high frequencies, the skin effect means that RF energy only penetrates a thin surface layer of a conductor. At low frequencies—particularly below 1 MHz—magnetic permeability becomes more important, and higher-permeability materials like steel outperform highly conductive materials like copper and aluminum.

The practical implication: at the frequencies used by MRI scanners (64 MHz for 1.5T, 128 MHz for 3T), all three materials perform similarly if properly constructed. At lower frequencies—below 1 MHz, relevant for magnetic interference and some EMP scenarios—steel's higher permeability gives it an advantage over copper and aluminum.

Copper RF Shielding

Performance Characteristics

Copper is the highest-conductivity commercial shielding material, which gives it excellent performance at high frequencies. For MRI RF cages, EMC test chambers, and signal isolation rooms where the shielding requirement extends above 1 GHz, copper provides reliable, well-characterized attenuation.

Copper is also highly workable—it can be soldered, bent, and formed with standard tools, which simplifies penetration sealing and joint construction. Solder joints in copper cages provide continuous electrical bonding that is difficult to achieve as reliably with mechanical fasteners alone.

Cost Profile

Copper is the most expensive of the three materials on a per-square-foot basis. Material cost for copper shielding panels runs approximately 2–3x that of galvanized steel for equivalent panel area. This premium is justified in high-specification applications where maximum conductivity or solder-joint reliability is required.

Best Applications

Copper is the preferred material for MRI RF cages at most major scanner manufacturers' specifications, high-specification EMC test chambers requiring attenuation above 100 dB, and environments where long-term corrosion resistance without surface treatment is valued.

Galvanized Steel RF Shielding

Performance Characteristics

Galvanized steel has lower electrical conductivity than copper but higher magnetic permeability—which gives it better low-frequency shielding performance. For applications that require attenuation below 1 MHz (certain EMP scenarios, power frequency interference, or low-frequency magnetic field containment), galvanized steel outperforms copper at equivalent thickness.

At MRI frequencies (64–300 MHz) and above, galvanized steel performs comparably to copper when panels and joints are properly constructed. Most shielding effectiveness specifications for commercial MRI applications can be met with galvanized steel at a lower material cost.

Cost Profile

Galvanized steel is typically 30–40% less expensive than copper for equivalent-area RF shielding. This makes it the dominant material for cost-sensitive MRI applications, large EMC test chambers, and government/defense shielded rooms where copper is not specifically required.

Best Applications

Galvanized steel is appropriate for MRI RF cages where copper is not explicitly required by the scanner manufacturer, large-format shielded rooms and EMC test chambers, applications requiring low-frequency magnetic shielding performance, and SCIF construction where cost efficiency is a priority.

Aluminum RF Shielding

Performance Characteristics

Aluminum's electrical conductivity is approximately 60% that of copper—lower than copper but sufficient for high-frequency RF shielding applications. Its major practical advantage is weight: aluminum is approximately one-third the density of steel and one-third the density of copper, making it valuable in applications where structural load is a constraint.

Aluminum does not have the magnetic permeability of steel, which limits its low-frequency performance. It also cannot be soldered using conventional techniques, which means all joints must be achieved through mechanical means (gaskets, overlapping panels, and conductive adhesive tapes). This makes penetration and joint construction more demanding.

Cost Profile

Aluminum falls between copper and galvanized steel on a cost-per-weight basis, but its lower density often means lower total material cost for large installations. Installation labor may be lower due to reduced panel weight. However, the mechanical joint requirement can increase labor time for complex penetrations.

Best Applications

Aluminum is the preferred material for pre-engineered relocatable shielded enclosures, applications in upper floors or structures with limited structural capacity, portable or temporary shielding installations, and aerospace or defense applications where weight is a primary constraint.

Property	Copper	Galvanized Steel	Aluminum
Electrical conductivity (relative)	Highest (100%)	Moderate (~17%)	High (~61%)
Magnetic permeability	Low	High (ferromagnetic)	Low
Low-frequency shielding (<1 MHz)	Moderate	Best	Moderate
High-frequency shielding (>100 MHz)	Best	Very Good	Very Good
Weight (relative)	Heavy	Heaviest	Lightest
Relative material cost	Highest	Lowest	Middle
Solder-joint capability	Yes	Difficult	No (conventional)
Corrosion resistance	Excellent	Good (with galvanizing)	Very Good
Primary use case	MRI rooms, high-spec EMC chambers	Cost-optimized MRI, SCIFs, large chambers	Relocatable enclosures, weight-constrained

Best Material for RF Shielding Rooms: Application Guide

For clinical MRI installations at 1.5T and 3.0T, copper is typically specified by scanner manufacturers and is the industry standard for new construction. Galvanized steel is acceptable for some manufacturers' specifications and is commonly used in cost-sensitive projects.

For EMC test chambers requiring attenuation across a wide frequency range (typically 10 kHz to 18 GHz or higher), the material is usually selected based on the specific frequency range of concern and the required attenuation levels. High-specification chambers often use copper for frequencies above 1 GHz and supplement with mu-metal or silicon steel for low-frequency performance.

For SCIF construction, galvanized steel is commonly used as the primary shielding material. The specific material requirements are defined by the SCIF Tech Spec and the cognizant security authority.

For EMP/HEMP protection, steel's magnetic permeability provides better low-frequency attenuation than copper or aluminum at equivalent thickness. MIL-STD-188-125 certified facilities typically use steel as the primary material.

Material Thickness and Shielding Effectiveness

Within a given material, increasing thickness improves shielding effectiveness—but with diminishing returns. The relationship is governed by the skin depth of the material at the frequency of concern. For most RF shielding applications, panel thickness is driven by structural requirements (panel rigidity and installation stability) rather than electromagnetic performance alone.

Standard panel gauges for commercial RF shielding rooms:

• Copper: 20 gauge (0.032") to 16 gauge (0.059") standard; heavier gauges for high-specification installations
• Galvanized steel: 20 gauge (0.036") to 14 gauge (0.075") standard
• Aluminum: 0.040" to 0.080" common for pre-engineered enclosures

Frequently Asked Questions About RF Shielding Materials

What is the best material for RF shielding?

There is no single best material—the optimal choice depends on frequency range, application, structural constraints, and budget. Copper is best for high-frequency performance and MRI applications; galvanized steel excels at low-frequency magnetic shielding and is cost-effective for large rooms; aluminum is best for relocatable and weight-constrained installations.

Is copper or steel better for RF shielding?

Copper provides better high-frequency conductivity; steel provides better low-frequency magnetic shielding due to its ferromagnetic permeability. For MRI RF cages (64–300 MHz), both perform adequately—copper is typically preferred by scanner manufacturers but galvanized steel is widely used in cost-optimized projects.

What is the best material for an RF shielding room?

For clinical MRI: copper is most commonly specified. For large EMC test chambers: galvanized steel is common due to cost efficiency. For SCIF construction: galvanized steel is standard. For portable or relocatable enclosures: aluminum is preferred for its weight advantage.

Does aluminum provide good RF shielding?

Aluminum provides very good high-frequency RF shielding, with conductivity approximately 61% that of copper. It is not suitable for applications requiring low-frequency magnetic shielding (below 1 MHz) due to its low magnetic permeability. Its primary advantage is weight—it is one-third the density of steel.

What gauge should RF shielding panels be?

Standard commercial RF shielding rooms typically use 20–16 gauge copper or 20–14 gauge galvanized steel. The specific gauge is selected based on structural panel rigidity requirements and the shielding effectiveness specification. Your contractor should specify the gauge in their proposal with reference to the intended performance level.

How do I specify RF shielding materials in an RFP?

Specify the material type (copper, galvanized steel, or aluminum), minimum panel gauge or thickness, applicable material standard (e.g., ASTM A653 for galvanized steel), and any surface treatment requirements. If material substitutions are permitted, define the equivalence criteria—typically equivalence of shielding effectiveness test results rather than material properties alone.

Is galvanized steel as effective as copper for MRI shielding?

For MRI RF cage applications at clinical field strengths (1.5T and 3.0T), galvanized steel meets the shielding effectiveness requirements of most scanner manufacturers' specifications. Copper is preferred by some manufacturers and required by others—always verify with the specific scanner manufacturer's site preparation documentation.