Use Nationally and in Massachusetts
Manufacturers produce hydrofluoric acid from the mineral fluorspar. Three manufacturers--Allied Signal, DuPont, and Elf Atochem North America--produce hydrofluoric acid in the U.S. They had the capacity to produce 211,000 tons of hydrofluoric acid in 1994. The major U.S. markets for hydrofluoric acid are fluorocarbon production (46%), aluminum production (21%), chemical derivatives (13%), petroleum alkylation catalysis (4%), metal surface treatments--pickling and desmuting (4%), uranium production (3%), and other uses, which include the etching of silicon (9%).
- Hydrofluoric acid is an intermediary in the manufacture of fluorocarbons. Prior to the 1987 Montreal Protocol, chlorofluorocarbons (CFCs) were the dominant fluorinated hydrocarbon. Today, hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs) are the dominant fluorocarbons.
- Aluminum manufacturers use cryolite, manufactured from hydrofluoric acid, in the smelting of primary aluminum.
- The major chemical derivatives manufactured from hydrofluoric acid are fluoropolymers, inorganic fluorides, fluoborate salts, fluoboric acid, and fluoborates.
- Petroleum alkylation catalysis is a process for producing high-octane components for use in motor fuels. Hydrofluoric acid is the catalyst in this process.
- Hydrofluoric acid is used in metal surface treatments, including pickling and desmuting. Metal pickling is the process by which manufacturers remove surface oxides (scale) from stainless steel and other metals. A variety of acids can be used to accomplish this task, including nitric and sulfuric acids. Hydrofluoric acid is normally used for the pickling of stainless steel. Desmuting is necessary to remove the gray-to-black residual film deposited on the surface during cleaning and etching processes. Hydrofluoric acid is used for desmuting high-silicon aluminum alloys and aluminum die castings.
- Uranium manufacturers use hydrofluoric acid to produce uranium hexafluoride; it separates U-235 from other uranium isotopes for use in nuclear reactors.
- The primary "other" use of hydrofluoric acid is etching. Etching prepares the surface for further processing in various ways, including increasing wettability, changing the appearance or texture of the finish and removing contaminants. The primary use for etching is for silicon in the manufacture of microelectronic circuits. The electronics industry uses high-purity 49% hydrofluoric acid solution to etch silicon.
Massachusetts facilities reported using 640,000 pounds of hydrofluoric acid in 1996 (see Table 1). In Massachusetts metal cleaning (pickling and desmuting) and etching applications accounted for 75% of reported hydrofluoric acid use (see Table 2).
- Metal cleaning (pickling and desmuting) is the primary end-use for hydrofluoric acid in Massachusetts. These applications consumed 50% of all hydrofluoric acid use in 1996.
- Etching applications consumed 26% of the state's reported hydrofluoric acid use.
- Hydrofluoric acid is also incidentally "manufactured" by coal-fired power plants. Coal contains minute levels of fluorspar which are converted to hydrofluoric acid during combustion. These facilities, which began reporting in 1991, accounted for 24% of HF use in 1996.
Hydrofluoric acid use in Massachusetts declined slightly, by 5%, between 1990 and 1996. Excluding power plants, who were first required to report in 1991, hydrofluoric acid use declined by 28% between 1990 and 1996. Etching use declined by 43% and metal cleaning use declined by 15%. HF manufactured by power plants decreased by 17% from 189,000 in 1991 to 157,000 in 1996.
Table 1 includes two sources of "output" data: MA TURA and U.S. Environmental Protection Agency (EPA), Toxics Release Inventory (TRI) data. The MA TURA database includes all non product material created by a process line prior to release, on-site treatment, or transfer ("byproduct") and the amount of toxic chemical incorporated into a product ("shipped in or as product"). The U.S. EPA, TRI database includes information on the waste materials generated by a facility after on-site treatment including: releases to air, land, and water ("environmental releases") and transfers off-site for treatment or disposal ("off-site transfers").
- MA TURA "byproduct" outputs grew by 12% due to the additional reporting of power plants (145,000 pounds in 1996) and increased byproduct generation by Allegro Microsystems, Crown Cork and Seal, and Rodney Metals. Byproducts probably increased for Allegro (25,000 pounds) and Crown Cork and Seal (58,000 pounds) because they incorrectly reported byproduct for 1990, the first year of reporting. Byproduct increased for Rodney Metals due to increased use of hydrofluoric acid.
TRI releases and transfers are much less than TURA outputs because the majority of hydrofluoric acid is treated on-site (neutralized) before being discharged.
- Off-site transfers declined dramatically due to reductions by Rodney Metals (49,000 pounds), Wyman Gordon (70,000 pounds), and Osram Sylvania (99,000 pounds). The Osram Sylvania plant closed in 1995. The Wyman Gordon facility in Worcester stopped reporting hydrofluoric acid use in 1993 (it accounted for 32,000 pounds of hydrofluoric acid offsite transfers in 1990).
- The increase in environmental releases is due to air emissions from power plants, which were required to report in 1991.
The national chemical use data are from Stanford Research Institute (SRI) International, 1995, Chemical Economics Handbook, "Fluorine Compounds" (Palo Alto, California: SRI). The Massachusetts chemical use data are from the Massachusetts Department of Environmental Protection (MA DEP), 1998, "Massachusetts Toxics Use Reduction Act Chemical Reporting Data" (Boston: MA DEP).