May, 29 2018

Nickel-Aluminum EMI Silicone Resists Galvanic Corrosion

Nickel-Aluminum EMI Silicone Resists Galvanic Corrosion

Specialty Silicone Products (SSP) supplies a nickel-aluminum silicone that provides EMI shielding, resists galvanic corrosion, and offers an offset to Chomerics 6502. SSP-2529 is ideal for marine environments and is available in molded sheets and extruded profiles. SSP’s dark gray, 68-durometer shielding silicone also has shorter lead times and lower minimum order quantities (MOQs) than the competition. 

The shielding effectiveness for SSP-2529 was tested at over 100 dB between 20 MHz and 2000 MHz per MIL-DTL-83528F. Test results from an independent, third-party laboratory report a minimum attenuation level of 93 dB at 10 GHz and a best-case attenuation level of 135 dB at 80 MHz. 

SSP-2529 was also tested according to ASTM B117, which defines a standard practice for operating a salt spray apparatus. Galvanic corrosion testing involved 168 hours of salt spray exposure at 95° F. The weight loss of the aluminum sample was only 0.08%.

EMI Gaskets and Galvanic Corrosion

SSP-2529 is filled with nickel-coated aluminum particles that provide EMI shielding and electrical conductivity. Compared to other EMI elastomers, nickel-aluminum silicones deliver the highest shielding effectiveness after long-term age testing. These particle-filled elastomers also have low transfer impedance and are a great choice for flange gaskets that require galvanic corrosion resistance.

Typically, EMI gaskets are installed between flanges that are made of different metals than the gasket’s fill material. In marine environments, fluids collect at the flange-gasket interface. This creates a galvanic cell where a loss of material occurs at the least corrosion-resistant metal. Eventually, the pitting that’s associated with galvanic or bimetallic corrosion can shorten flange life and even cause flange failure.

EMI Shielding and Galvanic Stability

SSP-2529 was tested for EMI shielding effectiveness by D.L.S. Electronic Systems of Wheeling, Illinois, a MIL-DTL-83528 certified laboratory. SSP’s nickel-aluminum silicone was also subjected to galvanic corrosion testing in a salt fog chamber. The material under test was aluminum 6081 with a chromate conversion coating per the U.S. military’s MIL-DTL-5541F standard.        

The EMI shielding report for SSP-2529 is available via the SSP website and summarized in a white paper called “Nickel-Aluminum Silicone for Corrosion-Resistant EMI Gaskets”. This SSP publication also provides galvanic corrosion test results and material properties such as tensile strength, elongation, thermal stability range, and thermal conductivity.

Get the White Paper

Engineers and technical buyers who would like to learn more about SSP-2529 are encouraged to view the EMI Shielding Report and request SSP’s white paper. To get your copy of “Nickel-Aluminum Silicone for Corrosion-Resistant EMI Gaskets”, contact SSP on-line or email Dominic Testo.