The bipolar plate is the structural, current-carrying separator between adjacent cells in a fuel cell stack, and the coating is a thin surface layer applied to it to cut electrical contact resistance and resist corrosion in the stack's humid, acidic operating environment. Coating chemistry and deposition method are patented separately from the plate substrate because the same base plate (steel, titanium, composite) can be paired with very different coating systems, each with its own performance and cost trade-off. That is why this landscape tracks IPC classes like C23C (coating and surface deposition) and B05D (coating processes) alongside the parent fuel cell class H01M rather than treating plate and coating as one invention.

The ranking covers 55 companies across the 109 records in scope, with the leader holding 10 records, fifth place holding 5 and tenth place holding 4. The top 5 assignees combine for 31.2% of all records and the top 10 for 53.2%, which means ownership is fragmented rather than dominated by one or two firms. Automotive OEMs, plate and gasket component suppliers, and a scattering of steel manufacturers make up the bulk of the ranked list, with the remaining companies each holding only a handful of filings.

Filings peaked at 13 records in 2021 and fell to 4 by 2024, a decline of 69% over that three-year span using complete-year data. Because patent publication typically lags filing by around 18 months, the 2025 and 2026 figures in any dataset are still incomplete and should not be read as evidence of a further drop. Taken together, the reliable trend shows a filing peak that has already passed rather than a market still accelerating.

This GM Global Technology Operations record, published in 2009, claims a method of selectively depositing a low-contact-resistance material onto portions of the lands of a bipolar plate's flow field while deliberately leaving other land areas uncovered. The narrow point is the selectivity: it is a patterned, partial-coverage deposition rather than a blanket coating over the entire plate surface. A design that applies uniform full-surface coating, or that patterns coverage on channels rather than lands, sits outside this specific claim, though a full freedom-to-operate check should compare the exact claim language against the intended process.

The clearest gap is the imbalance between the fuel cell parent class H01M, present on 96.3% of the 109 records, and the coating-specific classes sitting underneath it: C23C at 19.3%, B05D at 12.8%, and B32B and C23F each at 6.4%. That gap suggests many records claim a coated bipolar plate at a general level without deep, dedicated coating-process or corrosion-resistance claims, leaving room for narrowly drafted coating-composition and deposition-process claims that current filings have not staked out. Combined with a fragmented ownership structure — no filer holds more than 10 of 109 records — a well-drafted claim in the coating-process layer has a reasonable chance of clearing prior art.