Fortunately, these numbers are fairly easy and inexpensive to achieve if approached in the proper manner. The initial goal should be to reduce the Cr(VI) at its source by the use of Fume Suppressants or a Low Cr/High Efficiency Bath. Depending on the operation, both of these may be needed.
5 Products That Will Help You Meet The New OSHA - PEL For Chrome
Fume Suppressants
Fume suppressants can reduce the chrome mist by over 99%. The surface tension should be controlled at 35 dynes/cm, or lower, for maximum effect. Plating Resources, Inc. offers four (4) fume suppressants; a non-foam, a low foam, a medium foam and a high-foam version. These are based on fluoropolymer technology and do not break down or contaminate the bath. These are the lowest cost permanent fume suppressants available.
| ST-45: | Medium-Foam | Extremely low cost |
| FS-600: | High-Foam | Thick dense foam blanket. |
| FS-750: | Low-Foam | Concentrated & low usage. |
| FS-900: | Non-Foam | Best for high solution levels. |
Low Cr/High Efficiency Bath
A new bath additive is available that allows plating with only 20 oz/gal. of chromic acid. This results in a mist reduction of 40%. Bath conversions are done by simple dilution. An additional benefit is that this bath plates 30% faster. When used along with a Fume Suppressant, a 99% and a 40% reduction from the old 52 ug standard would result in only 0.624 ug of CR(VI). The Low Concentration/ High Efficiency bath is somewhat less conductive so higher voltages are needed. Contaminated baths using rectifiers at maximum voltage will plate at lower speeds, so some thought should be given to replacing these baths with a fresh solution. This is less expensive than buying a new rectifier and will also result in the higher quality deposits and faster plating rates that the new bath provides.
Chrome Kill
Industrial hygienists feel that spray rinsing directly over the chrome tank causes excess Cr(VI) exposure. The solution is to adopt a revised rinsing cycle that uses Chrome Kill-318 in a final hot rinse. The best design uses an empty tank for initial spray rinsing (down inside the tank) so the chrome mist is contained and the rinsate can be pumped back into the bath for recovery. The part(s) are then immersed in a 1-2 oz/gal. Chrome Kill-318 rinse operated at 90-150 degrees. This “kills” all of the hexavalent chrome on the parts, which prevents staining and provides fast drying. In many cases the parts are de-racked over the Chrome Kill-318 tank and immersed again before they are allowed to dry. The Chrome Kill-318 bath has a long life, but eventually will require re-making.
Chrome Kill-318 can also be used other ways to reduce Cr(VI) exposure in the workplace. It is used both in the powder form directly for chrome spills and as a liquid for stains on parts and equipment. It is important to eliminate all of these sources as working (even walking) in a chrome dust laden area can cause Cr(VI) exposure.
Anode Cleaner
Hygienists also feel that hand cleaning lead alloy anodes causes excess Cr(VI) exposure. The solution is to use an anode cleaner tank. AnoBest-104 is an alkaline soak cleaner for lead alloy anodes that remove the chromate film and scale without the employee having to do this manually, thereby reducing exposure. Anodes can be stored in this solution indefinitely until needed which also keeps the shop cleaner and more organized.
Clean anodes plate faster which means less time in the tank and less chrome exposure. A bare steel tank is all that is needed which may be heated if required. The AnoBest-104 bath has a long life, but eventually will require re-making.
Technical Assistance
Contact us for other suggestions on the best approach for meeting the new Cr(VI) limits. We can send you a complimentary copy of our “Guidance Outline” which provides additional information. We can also help you by providing:
2. Ventilation Systems♦ Assistance with the regulations.
♦ Developing an Action Plan.
♦ Reducing Cr(VI) exposure.
♦ Low cost personal monitoring & analysis.
The plater is also required to maintain an Operation and Maintenance Plan (O&M Plan) as part of the permitting requirements. The O&M Plan limits the maximum amount of amperes and hours of production per year, specifies the inspection frequency, details the maintenance procedures has provisions for malfunctions and corrective actions, and states the record keeping requirements, among other items. In most cases the O&M plan is provided by an outside consultant due to its complexity.
The air discharge permits require that initial stack testing be performed in order to prove compliance with the maximum discharge limitation. In some cases future stack testing may even be required at specified intervals. The cost to perform stack testing varies with the geographical location, but typically is around $2,500 – 4,000 per stack.
In addition, the plater can expect that periodic inspections will be held by the control authority to ensure that, the O&M Plan is being followed and the air discharge limit is not being violated. Fairly hefty fines can be levied in the event of violations, especially deliberate and frequent ones.
Due to a number of factors, it can sometimes be difficult to maintain the chrome discharge below the permitted limit. There are several “tricks” that the plater can use to assist with this:
Use a lower solution level.
The trend today is to use a much lower solution levels in the plating tanks. The typical 2-4” level is being lowered to as much as 12” as measured from the tank rim to the bath surface. This greatly assists in keeping a majority of the chrome mist in the tank and out of the ventilation system while also keeping the rim and buss much cleaner. The only downside is the need to use longer fixtures and anode leads.
Use a lower concentration bath.
Using a 20 oz/gal. bath will reduce chrome emissions by around 40% from a 30 – 40 oz. bath. The use of a Dura Additive will provide the same plating quality as a higher concentration bath will. The only downside is that low concentration baths are more sensitive to contamination, particularly trivalent and iron. This may lower the available amperage if the rectifier is at its maximum voltage. If the bath is relatively clean, then a low concentration bath should be considered. In many cases the use of Dura-76 which chelates contamination will be of great help with this.
Lower the surface tension.
A permanent fume suppressant (wetting agent type) like Cancel ST-45 can be used to lower the baths surface tension which will reduce the chrome emissions by as much as 95%.
Reduce air agitation.
Install a timer on the air agitation pump so that it operates for only 15 seconds every 5 minutes. This is enough time to maintain bath uniformity and it significantly reduces the chrome emissions from the tank. If the agitator is operated continuously then the air volume should be reduced.
Raise bath temperature.
Increase the bath temperature to 140 – 145 def. F., but don’t exceed the limit of the tank lining. Most linings will stand 145 deg. continuous usage without damage. Higher bath temperatures reduce the emissions by increasing the efficiency.
Contact us to arrange for a low cost testing with a calibrated sampling pump and an OSHA approved analysis of the Cr (VI) in the shop air.