Rosin fluxes are categorized by grades of activity: L for low, M for moderate, and H for high. There are also other abbreviations for different rosin flux grades:
* R (Rosin) – pure rosin, no activators, low activity, mildest
* WW (water-white) – purest rosin grade, no activators, low activity, sometimes synonymous with R
* RMA (rosin mildly activated) - contains mild activators, typically no halides
* RA (rosin activated) – rosin with strong activators, high activity, contains halides
* OA (organic acid) – rosin activated with organic acids, high activity, highly corrosive, aqueous cleaning
* SA (synthetically activated) – rosin with strong synthetic activators, high activity; formulated to be easily soluble in organic solvents (chlorofluorocarbons, alcohols) to facilitate cleaning
* WS (water-soluble) – usually based on inorganic or organic halides; highly corrosive residues
* SRA (superactivated rosin) – rosin with very strong activators, very high activity
* IA (inorganic acid) – rosin activated with inorganic acids (usually hydrochloric acid or phosphoric acid), highest activities, highly corrosive
R, WW, and RMA grades are used for joints that can not be easily cleaned or where there is too high corrosion risk. More active grades require thorough cleaning of the residues. Improper cleaning can actually aggravate the corrosion by releasing trapped activators from the flux residues.