Copper Electrorefining Patents: Top Companies & Trends 2026
- 22.5% concentration. The top five assignees account for 214 of 950 records in scope — a concentrated core against a long tail of single- and few-filing entrants.
- Filing peaked in 2020. Volume reached 43 records that year; by the last complete year, 2021-to-2024 filings fell 69%, from 16 to 5.
- C25C dominates the class mix. 58.8% of records sit in electrolytic metal production (C25C), with electroplating (C25D) a distant second at 31.6% — refining process claims outweigh surface-finish claims by a wide margin.
Filing growth compares 2021 (16 records) with 2024 (5) — a three-year span. 2024 is the most recent year we treat as complete: publication lags filing by roughly 18 months, so 2025 onwards are still filling in and any growth rate that ends there would understate the field. Top-5 share is the combined record count of the five largest assignees divided by all 950 records in scope (CR5), not by the ranked leaders only.
What this landscape covers
This dataset tracks 950 published records filed or published between 2015 and mid-2026 that combine copper electrorefining, anode slime or copper cathode quality terms with a technical control mechanism — current density, electrolyte additive, nodulation control, short-circuit detection, permanent cathode or cathode stripping machine. That pairing narrows the field to records where a refining process claim is tied to an operational control, rather than to general copper metallurgy.
The scope spans six receiving offices, led by the United States and Japan, and the assignee ranking returned by the data endpoint covers 100 companies. Because publication trails filing by roughly 18 months, the most recent one to two years in any trend chart will read lower than the true filing volume once those applications publish.
Filing trend and technology composition
Two views of the same 950 records: how filing volume has moved year over year, and which IPC subclasses carry the claims.
Filing trend, 2017–2026
Filings rose to a peak of 43 records in 2020, then declined; over the last fully-published three-year span the count fell from 16 in 2021 to 5 in 2024, a 69% drop. 2025 and 2026 figures are still incomplete due to publication lag and should not be read as a continuation of that decline.
IPC subclass distribution
C25C (electrolytic metal production) covers 58.8% of the 950 records, well ahead of C25D electroplating and electroforming at 31.6% and C22B metal extraction and refining at 18.0%. Smaller shares in C22C alloys, C25B electrolytic compound production, G01N testing, H10P and B01D separation mark narrower, more specialised claim areas. Because records can carry multiple classes, these shares sum to more than 100% of the record total.
Shares are the percentage of the 950 records in scope. A patent can carry several IPC classes, so the shares add up to more than 100%.
Go deeper on Copper Electrorefining with Eureka
This page is one run against one query. Ask Eureka your own question about copper electrorefining and every answer comes back with the patent numbers behind it.
Try EurekaRepresentative and most-cited filings
US20210189576A1 — Improvement in copper electrorefining
A process for copper electrorefining that fixes the cell voltage below 1.6 volt, sets an anode composition of at most 98.0 wt% copper and under 1.00 wt% iron, runs current density at or above 180 A/m2 of cathode surface, refreshes electrolyte at 30-1900% per hour by overflow, and bubbles gas through the electrolyte between anode and cathode.Filed by Metallo Belgium; published 2021-06-24.
| # | Publication no. | Patent title | Citations |
|---|---|---|---|
| 1 | US3770598A | Electrodeposition of copper from acid baths | 249 |
| 2 | US20020006876A1 | Revolution member supporting apparatus and semiconductor substrate processing apparatus | 85 |
| 3 | US4146437A | Method for evaluating a system for electrodeposition of metals | 70 |
| 4 | US4158612A | Polymeric mandrel for electroforming and method of electroforming | 69 |
| 5 | JP1990185990A | Ultrahigh purity copper and production thereof | 65 |
| 6 | US5492608A | Electrolyte circulation manifold for copper electrowinning cells which use the ferrous/ferric anode reaction | 60 |
| 7 | JP1992317423A | Method for recovering platinum group metal | 58 |
| 8 | US6231742B1 | Electrolytic Copper foil and process for producing the same | 57 |
| 9 | US5622615A | Process for electrowinning of copper matte | 55 |
| 10 | US5384016A | Process for recovering tungsten carbide from cemented tungsten carbide scraps by selective electrolysis | 54 |
Citation counts accumulate over time and favour older filings; a low count on a recent record does not mean it is less significant, only less cited so far.
Each row carries its publication number; clicking a row searches Eureka by that number.
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Three read-throughs from the concentration, trend and citation figures above.
A concentrated core, long tail behind it
The leader alone holds 71 records, and the fifth-place assignee holds 30 — a steep drop-off. The top 10 combined reach 36.5% of all records, meaning the remaining 63.5% is spread across the rest of the 100 ranked companies plus unranked filers.
Volume has cooled since the 2020 peak
Filings ran at 43 in the peak year, 2020, then declined to 16 by 2021 and to 5 by 2024 — the last year with a reasonably complete publication record. That is a maturing filing curve, not necessarily a maturing technology; occupied claim space can just as easily explain reduced new filing.
Foundational electrodeposition art still anchors the field
The most-cited record in this set, US3770598A on electrodeposition of copper from acid baths, sits well ahead of the next most-cited filing. Heavy citation of an older foundational patent signals a crowded prior-art baseline for basic electrodeposition claims, pushing new filings toward narrower operational controls.
Eureka can read the same corpus for gaps instead of for coverage: under-claimed branches adjacent to copper electrorefining, with the prior art for and against each one.
Who is filing, and what is still open
The ranked leaders sit alongside smelting and materials groups with single-digit filing counts; recent-year momentum for the top names has dropped to zero, consistent with the field-wide slowdown after 2020.
One assignee well ahead of the field
The leading assignee's 71 records put it more than double the fifth-place holder's 30, a gap that suggests a deliberately built portfolio around core electrorefining process controls rather than incidental filing.
A tighter cluster from fifth to tenth
The gap from fifth place (30) to tenth place (23) is much narrower than the gap from first to fifth, indicating a cluster of comparably-sized portfolios competing just below the top tier.
Co-filing is limited and concentrated
Only 10 co-assignee pairs appear across the dataset, and the strongest of these ties two related corporate entities rather than independent companies — cross-company joint filing is not a major feature of this field.
| Assignee | Recent year | YoY |
|---|---|---|
| M & T Chemicals Inc. | 0 | — |
| Mitsubishi Materials Corporation | 0 | — |
| Outokumpu Oy | 0 | — |
| Phelps Dodge Corporation | 0 | — |
| ASARCO LLC | 0 | — |
| Metallo Belgium | 0 | — |
| Outotec Oyj | 0 | — |
| Sumitomo Metal Mining Co., Ltd. | 0 | — |
Where to take this analysis
The dataset points to a few concrete next steps depending on whether you are scoping freedom-to-operate, evaluating a licensing target, or deciding where to file.
Map the leader's full claim scope
With 71 of 950 records, the top assignee's portfolio warrants a dedicated claim chart before any new filing in current density or electrolyte additive control.
Explore assignee portfolios in EurekaWatch the under-claimed branches
Short-circuit detection and permanent cathode coating claims show thinner density than the core C25C process claims — a plausible entry point for a narrower, defensible filing.
Run a white space search in EurekaRe-check the trend once 2025-26 publishes
The apparent post-2020 decline is partly a publication-lag artefact; revisit the filing curve once the most recent two years finish publishing before concluding the field has gone quiet.
Track filing trends in EurekaCommon questions on copper electrorefining patents
One assignee leads the ranked field with 71 of the 950 records in scope, more than double the fifth-place holder's 30. The top five combined account for 22.5% of all records, and the top ten reach 36.5% — a concentrated core with a long tail of smaller filers across the remaining ranked companies. Anyone assessing competitive position should look at both the leader's scope and the tighter cluster sitting just below it, since the gap from fifth to tenth place is comparatively small.
Filing peaked at 43 records in 2020 and has fallen since, with the last fully-published three-year span showing a drop from 16 filings in 2021 to 5 in 2024, a 69% decline. That decline should not be read as the field going quiet, though: publication typically lags filing by around 18 months, so 2025 and 2026 counts are still incomplete. A fair read is that filing has cooled from its 2020 peak, not that current activity has stopped.
Electrolytic metal production (IPC class C25C) covers 58.8% of the 950 records, by far the largest share, followed by electroplating and electroforming (C25D) at 31.6% and metal extraction and refining (C22B) at 18.0%. Narrower classes such as alloys, electrolytic compound production, material testing and separation processes each cover under 7% of records. Since a single record can carry multiple IPC codes, these shares add up to more than 100% of the total record count.
This Metallo Belgium filing, published mid-2021, describes a copper electrorefining process that constrains cell voltage below 1.6 volt, sets anode composition limits (at most 98.0 wt% copper, under 1.00 wt% iron), runs current density at or above 180 A/m2 of cathode surface, refreshes electrolyte at 30-1900% per hour by overflow, and introduces gas bubbled between anode and cathode. It is a process-parameter patent rather than a new electrodeposition mechanism, so it is most relevant to anyone designing a cell operating within those specific voltage, composition and current density ranges.
Relative to the dense core of C25C process claims, areas such as real-time short-circuit detection, permanent cathode surface coatings, and electrolyte additive dosing control show thinner filing density in this dataset. These are not unclaimed, but they carry fewer competing filings than the core current-density and voltage-control claims that dominate the top assignees' portfolios. A narrowly scoped filing tied to a specific sensor method or coating chemistry in these branches has more room to clear prior art than a general electrorefining process claim.
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Disclaimer. This page is generated from Patsnap Eureka data drawn from a limited snapshot of global patent and scientific-literature records, and is provided for general information and reference only.
Patent data carries inherent limitations: recent filings (typically the most recent 18–24 months) are under-counted due to standard publication lag; counts may be reported at either a patent-family or a patent-record basis and are not always directly comparable; classification, applicant-name, and citation data may contain errors, duplicates, or omissions; and the underlying search query defines and constrains the scope shown. As a result, the analysis may be incomplete or inaccurate and may not reflect the full technology landscape.
Nothing on this page constitutes an exhaustive prior-art, novelty, freedom-to-operate, or validity search, nor does it constitute legal, financial, investment, or professional advice, and it should not be relied upon as such. Any patent, commercial, or strategic decision should be verified independently and reviewed with qualified patent, legal, and domain professionals. Patsnap makes no warranties, express or implied, as to the accuracy, completeness, or fitness for any particular purpose of the information presented.
Machine translation. Assignee and organisation names originally recorded in Chinese, Japanese or Korean have been rendered into English by an AI translation step so that the tables stay readable. These renderings are best-effort and may not match a company’s registered English name; the original name is what the underlying patent record carries, and it is what any Eureka query launched from this page uses.