High HF resistant pH sensors for HF neutralization - Case Study
- Improved HF treatment system efficiency through more accurate pH measurement and control
- Reduced Sensor Usage through less usage
- Increased inline service time for sensors during specialized reference
An aluminum can etching company and a silicone wafer etching wanted to effectively treat their waste using a traditional CaF2 removal system. To efficiently add calcium hydroxide or calcium chloride, a pH sensor must be used to control this addition. The typical coating of the pH sensor under such conditions was exacerbated by the intermittent excursions into the low pH and high fluoride process media due to poor process control from failing sensors.
The poor performance of the previously used sensors accelerated their own demise by causing process excursions by a lack of addition of caustic (sensor became insensitive to pH change after coatings even with repeated cleanings), thus flooding the system over time with strong hydrofluoric acid, primed with either sulfuric acid (aluminum etching) or hydrochloric and nitric acid (wafer etching).