3 Minute Read
Out at sea, naval vessels become exposed to highly corrosive elements like saltwater which not only affects the hull and mechanical structures but can also compromise electrical conduits like grounding paths, cable terminals and junction points. Corrosion is a significant issue for naval ships, both deployed and docked and is a leading research topic within the U.S. Naval Research Laboratory.1
With antenna, radar systems and grounding planes along the ship’s deck, the saltwater exposure will over time cause these metallic instruments to oxidize. Coupled with the periodic sway of the ship, these structures can loosen from their base which impedes current flow, raising the contact resistance. If left unchecked, rising contact resistance risks sudden electrical discharge, posing threats to nearby instrumentation and crew aboard.
Various other grounding structures on the ship rely on mechanical fastening that mates two metallic surfaces. Under controlled, stable conditions of temperature and humidity, this setup works very well, providing a steady grounding path for current to dissipate. In the presence of an electrolyte like saltwater; however, this union of dissimilar metals produces a galvanic couple which can initiate corrosion along grain boundaries of common alloys like stainless steel.
The progressive oxidation of grounding structures leads to unscheduled maintenance and downtime. These problems are completely avoidable and add unnecessary costs for operation. Figure 1 below shows an example of a hybrid metal structure galvanically corroding
Figure 1: Example of galvanic corrosion aboard a naval vessel
Composite structures like modular masts and radomes are not as susceptible to systemic corrosion as are metals, given the inert materials they’re constructed from. They are also however, electrically insulating and therefore prone to static buildup with continued exposure to friction. Charge buildup along these surfaces can be problematic, risking sudden electrical discharge.
Non-Metallic Conductive Coatings Prevent Corrosion and form Conductive Pathways
For all situations mentioned above, conductive coatings made from non-metallic fillers like carbon and graphite provide a turnkey solution that not only protects against corrosion but also maintains an electrical path between 2 conductors. Because carbon is a nonmetal it does not corrode when exposed to salts and moisture and can mitigate galvanic degradation when used as an intermediate conductive layer with common architectural metals like aluminum and stainless-steel alloys.
Amorphous carbon and allotropes like graphite are also electrically conductive which is an especially important feature for preserving grounding systems. Amorphous carbon has sufficient conductivity for most grounding applications though it is insufficient for shielding against electromagnetic interference (EMI) at frequencies above about 10 MHz. Graphite (a 2D sheet-like structure of carbon) has many of the same features, with superior conductivity and shielding.
Conductive coatings made from carbon and graphite are a quick and easy way to render surfaces of insulating materials like plastics and composites sufficiently conductive for static dissipation and grounding. Unlike highly conductive coatings for EMI shielding, carbon and graphite are more suitable materials to bleed off excess current.
Properties of Carbon-Based Conductive Coatings
When compared to other conductive fillers used in electrically conductive coatings, carbon shows superior corrosion resistance, highlighting its suitability for ensuring longevity. Specifically, when subjected to salt fog conditions per ASTM B117 for seven days, carbon coatings show no loss in conductivity whereas more conductive fillers like nickel and copper showed decreases of 2X and 50X respectively.
Despite inferior sheet resistance and EMI shielding, carbon conductive coatings are an easy way to render insulators electrically conductive. The sheet resistance can be tuned by adjusting the film coating thickness, with surface resistance below 100 Ω/sq possible for carbon and about 25 Ω/sq for graphite. These material properties have been translated into coating systems.
MG Chemicals’ Carbon-Based Conductive Coatings
MG Chemicals has developed 2 acrylic conductive coatings using carbon flake technology. 838AR is a 1-part acrylic conductive coating formulated with carbon powder. The 839 coating is also a 1-part acrylic conductive coating that uses a more refined graphite flake. Both coatings have sufficient conductivity for fabricating and repairing grounding conduits while providing metallic parts with protection against corrosive elements.
For naval platforms that are continuously exposed to harsh, corrosive environments, maintaining reliable grounding pathways is essential for longevity. Carbon-based conductive coatings provide a durable, corrosion-resistant solution for a host of materials like metal interfaces and composites. implementing these coatings in maintenance programs can significantly reduce lifecycle costs while preserving electrical reliability.
-
Winget, E. (2025, June 13). NRL protects naval assets: Land, sea and air. CHIPS.
https://www.doncio.navy.mil/chips/ArticleDetails.aspx?ID=19312.
