Using conductive coatings in lightweight maritime electronics

This first guide in MG Chemicals' Practical Guide for Design Engineers series uses a representative sonobuoy electronics compartment to explain a practical method for evaluating conductive coatings.

In a compact sonobuoy electronics compartment, a low-level electrical signal from a hydrophone must remain usable while a telemetry radio, processor and switching power converter operate nearby. A polymer housing helps meet weight and packaging targets, but its wall contributes little electromagnetic shielding without a conductive surface.

A conductive coating can give a compatible non-metallic housing that surface. Effective shielding depends on the coating, the interference path, the substrate, the electrical interfaces and the exposure of the actual compartment.

The evaluation follows four stages: locate the interference path, create a continuous conductive boundary, select the coating for the actual exposure, and verify the weak signal in the operating assembly.

 

Stage 1: Locate the interference path

The hydrophone converts wanted sound into an electrical signal. Investigate how unwanted electromagnetic energy reaches the input circuitry while preserving the sensor's acoustic coupling and the intended antenna path. Candidate paths include radiation through the electronics housing, leakage at seams and openings, coupling onto cables, and noise conducted on power or return conductors.

Establish a baseline. Record the operating state and a functional measure such as noise floor, signal-to-noise ratio or a defined measurement error. A repeatable rise in front-end noise during telemetry transmission links the symptom to that operating state. Use controlled changes to shielding, cable routing or power connections to identify how the interference reaches the sensitive circuitry. Timing correlation alone does not distinguish radiated from conducted coupling.

Converter noise carried on supply lines may require filtering or layout changes as well as, or instead of, a coating.

 

Stage 2: Create a continuous conductive boundary

A conductive film supports induced currents on a surface that was previously insulating. Field attenuation depends on frequency, field conditions, coating conductivity and thickness, and enclosure geometry. Published material data helps select a candidate, but a complete housing adds covers, flanges, connectors and openings that can limit its shielding performance.

Specify coating coverage and dry-film thickness on the engineering drawing. Define masking and keep-out areas required for fit, electrical clearances and antenna operation, while retaining conductive surfaces needed at bonding and gasket interfaces. Specify how the coating connects to adjacent conductive structure.

Provide a repeatable conductive interface at each removable cover, using a suitable conductive gasket or other joint component where required. Define cable-shield termination and connector-shell contact at the enclosure entry.

Specify electrical continuity and environmental sealing as separate requirements for each joint. A watertight seam can still leak RF energy. Some conductive gaskets provide both functions. If relying on the conductive gasket as an environmental seal, qualify it for the required water or pressure sealing duty; shielding performance alone does not establish that capability.

Where the transmitter and sensitive front end share a compartment, coating the outer housing does not by itself prevent interference between those circuits. A coated local enclosure or conductive partition may be needed to interrupt internal radiated coupling. Place the shield according to the diagnosed path, and preserve thermal paths, fit and electrical clearances.

 

Stage 3: Select the coating for the actual exposure

Define the requirements before comparing products. Coating chemistry and filler affect conductivity, adhesion, process and durability, so evaluate their trade-offs against the actual compartment.

Interference band: Identify the frequencies that must be attenuated at the diagnosed path and the required level of attenuation.

Substrate: Check compatibility with the housing polymer and adhesion after the specified surface preparation.

Geometry and application: Establish whether the coating can be applied to a consistent dry-film thickness over the real edges, ribs and recesses.

Process: Confirm that production can support the required mixing, cure, masking and inspection.

Interfaces: Check that the coating makes reliable contact at covers, gaskets and connector shells.

Mechanical duty: Assess whether assembly, handling or abrasion could damage the film.

Environment: Identify what the coated surface will actually see, whether a protected interior, condensation, salt fog, cleaning fluids or immersion.

Distinguish an electronics compartment protected inside the product enclosure from a surface exposed directly to salt water, condensation or cleaning fluids. The coating supplies an electrical function; seals and the mechanical enclosure provide environmental protection. Neither a product family name nor a salt-fog rating proves suitability for immersion.

The 841AR and 842ER data sheets report favourable salt-fog ratings, but the applied finish still needs substrate-specific and assembly-level evidence. The 843ER data sheet reports poor salt-fog resistance; its mechanical hardness does not make it a general marine-exposure option. [1, 3, 4]

 

MG coating options for this application

841AR is a one-part, nickel-filled acrylic and a practical starting point for compatible plastic housings. Evaluate preparation, adhesion, coverage and attenuation in the required interference band.

842ER is a two-part, silver-filled epoxy that provides a durable conductive finish where a two-part process is acceptable. Qualify mixing, cure, interfaces and the actual environmental exposure.

842AR is a one-part, silver-filled acrylic to evaluate where relevant electrical data supports silver over nickel. Check performance in the required interference band, process fit and the complete enclosure.

These products are candidates for evaluation. Select from the current controlled product data and qualify the applied finish on the actual part. [1-3]

 

Stage 4: Verify the weak signal in the operating assembly

Repeat the functional measurement that revealed the original problem. Keep the normal cables, enclosure and operating modes, and use controlled comparisons to check whether the coating treatment reduces interference along the identified path.

Qualify surface preparation, adhesion, dry-film thickness and cure on representative parts. Repeat the functional measurement with telemetry, processing and power conversion running in the combinations that caused the problem.

Repeat critical checks after deployment, humidity, temperature, vibration or service exposures relevant to the intended duty. [7]

Equipment and system verification must follow the requirements, editions and test methods called up by the contract. A coating-panel result does not establish MIL-STD-461 or MIL-STD-464 compliance. [5, 6]

 

Discuss your application with MG Chemicals

No single coating suits every compartment: the diagnosed path, the joints and the real exposure decide the choice. MG Chemicals can help you evaluate coating candidates against your substrate, process and shielding requirements. Share the housing drawing and material, interference band, observed symptom, process limits and environmental duty so the discussion starts with the actual engineering problem.

 

Contact support@mgchemicals.com or visit https://mgchemicals.com/.

 

References

[1] MG Chemicals. 841AR liquid technical data sheet. Rev 7, 17 September 2026.
https://mgchemicals.com/downloads/tds/tds-841ar-l.pdf

[2] MG Chemicals. 842AR liquid technical data sheet. Rev 7, 17 September 2026.
https://mgchemicals.com/downloads/tds/tds-842ar-l.pdf

[3] MG Chemicals. 842ER kit technical data sheet. Rev 4, 17 September 2026.
https://mgchemicals.com/downloads/tds/tds-842er-2parts.pdf

[4] MG Chemicals. 843ER kit technical data sheet. Rev 7, 17 September 2026.
https://mgchemicals.com/downloads/tds/tds-843er-2parts.pdf

[5] DLA ASSIST. MIL-STD-461. Requirements for the Control of Electromagnetic Interference Characteristics of Subsystems and Equipment.
https://quicksearch.dla.mil/qsDocDetails.aspx?ident_number=35789

[6] DLA ASSIST. MIL-STD-464. Electromagnetic Environmental Effects Requirements for Systems.
https://quicksearch.dla.mil/qsDocDetails.aspx?ident_number=35794

[7] DLA ASSIST. MIL-STD-810. Environmental Engineering Considerations and Laboratory Tests.
https://quicksearch.dla.mil/qsDocDetails.aspx?ident_number=35978