In September 2012, following its residual risk and technology review (RTR) of the National Hazardous Air Emission Standards (NESHAP) for chromium electroplating and anodizing, the EPA issued revised regulations for the sector, which included a phaseout of the use of perfluorooctane sulfonic acid (PFOS) in wetting agent fume suppressants (WAFS) used in plating baths.
The RTR rule allows a 3-year compliance period—until September 21, 2015—for existing sources to eliminate the use of PFOS WAFS. Facilities can also apply for a 1-year extension to achieve compliance.
PFOS is a member of the long-chain perfluorinated chemical group that has been shown to be persistent, bio-accumulative, and toxic in the environment.
Chromium plating organizations have expressed concern about the phase-out, particularly as it affects small electropolaters that rely more on fume suppressants to reduce the surface tension of their baths, thereby lowering chromium emissions, than large facilities that rely more on emissions control equipment. The core of their complaint is that the non-PFOS WAFSs the EPA is advocating are not sufficiently effective in lowering chromium emissions, will cost significantly more than PFOS WAFSs, and will even compromise the plating process.
Lower surface tension
WAFS are used to lower the surface tension of electroplating baths. Lower surface tension, in turn, reduces the size of gas bubbles generated during electrolysis. The smaller bubbles travel more slowly through the solution and have less energy when they arrive at the solution’s surface. Lower surface tension also reduces the energy with which the resulting droplets are ejected into the air. Both effects can reduce the emission of droplets and, therefore, the amount of chromium emitted by the tank.
The RTR rule specifies that when a chemical fume suppressant containing a wetting agent is used, the surface tension of the electroplating or anodizing bath may not exceed 40 dynes per centimeter (dynes/cm) as measured by a stalagmometer or 33 dynes/cm as measured by a tensiometer at any time during tank operation. Compliance with the applicable surface tension limit ensures compliance with the emissions limit. Furthermore, as of the compliance date, no PFOS WAFS may be added to any affected hard chromium electroplating tank, decorative chromium electroplating tank, or chromium anodizing tank as a method to meet the NESHAP requirements for these source categories.
Facility reports
The Agency states that it has been reported that there are now “suitable, successful, and well proven” non-PFOS fume suppressants for hard and decorative chromium electroplating, and that the surface tension can be reduced to as low as 20 dynes/cm in baths, but is commonly maintained at about 30 dynes/cm. The Agency adds that PFOS WAFSs have been “seamlessly” phased out in Europe and Japan. Also, in preparing the RTR final rule, the Agency said it contacted several facilities that switched from PFOS-based fume suppressants to non-PFOS products.
The Agency said that one facility acknowledged that the non-PFOS WAFSs cost slightly more than the PFOS equivalents, but less of the non-PFOS product was needed. All the other facilities stated they noticed no difference in effectiveness, consumption, or required maintenance of the non-PFOS suppressant.
Emissions reduced?
Industry agrees that non-PFOS suppressants do lower surface tension but claims that the EPA has presented no data indicating the chromium emissions are actually reduced with the use of non-PFOS products. In other words, any additional risk associated with PFOS suppressants would be mitigated because of the reduction in chromium emissions; the same reasoning could not be applied to the use of non-PFOS suppressants, according to industry.
Industry has also argued that non-PFOS suppressants cost up to 30 percent more than PFOS suppressants and more frequent additions, more frequent monitoring, and more labor are needed to maintain the surface tension levels compared to the use of PFOS products. In addition, industry representatives say it can take a significant amount of time to test the use of non-PFOS suppressants on plated products and that the 3-year phase-in period is insufficient.
Performance differences
The EPA does not disagree that additional testing may be required to integrate the use of non-PFOS into operations, but believes that 3 years is adequate time to do so. Also, the Agency says industry has not presented details about why costs would be higher for any specific facility that switches to non-PFOS wetting agents. Further, the Agency does not agree that a reduction in surface tension will not result in a reduction in chromium emissions or that the surface tension reduction achieved by PFOS agents reduces emissions in ways that cannot be achieved by non-PFOS agents.
The EPA says that it acknowledges that there may be differences in the performance of non-PFOS-based fume suppressants in different types of chromium electroplating tanks, but adds that this is also true of PFOS-based fume suppressants.
“The performance of any type of fume suppressant can depend on the characteristics of the chemical and tank (i.e., temperature, contaminants present, etc.),” says the Agency, “but EPA has found no evidence that supports the idea that non-PFOS- based fume suppressants are unable to reach the surface tension limits being finalized in this rulemaking.”
Industry has also argued that EPA’s phaseout is unnecessary because the availability of PFOS suppressants is declining and occurrence of the product in plating baths will phase out without federal intervention. That point was equally ineffective in persuading the EPA to drop the required phaseout.
EPA’s final RTR rule was published in the September 19, 2012, FR.