Filing is concentrated: the five leading assignees together hold 44.4% of the 216 records in this dataset, and the ranked ten hold 69.0%. The single leading assignee holds 23 records, roughly a third more than the fifth-place holder’s 16. This pattern is typical of a chemistry-driven field where a handful of specialty water-treatment companies built portfolios early and later entrants filed in smaller numbers. Anyone assessing competitive risk should look at the leader’s specific claims first, since they cover the largest single block of prior art.

Filing peaked at 12 records in 2018 and has declined since; the tracked 2021-to-2024 measure shows a 100% drop, and the leading assignees report zero filings in the most recent year. That said, publication lags filing by roughly 18 months, so the last one or two years in any trend chart are always undercounted and should not be read as the final word. Taken together, the data through 2024 points to a genuine slowdown among the historic leaders rather than a data artefact.

The bulk of records classify under C02F (water and wastewater treatment, 67.1% of the 216 records) and C23F (corrosion and metal removal, 36.6%). Supporting classes include C09K materials, C08L polymer compositions, and smaller shares in analytical testing, heat-exchanger detail, separation processes and organo-metallic compounds. Because a single record can carry several IPC codes, these shares add up to more than 100% — they describe overlapping claim coverage, not a partition of the field.