Fluoride is added to drinking water in many areas as an important nutrient for the health of human teeth. Too much fluoride in the water, however, can lead to corrosion of pipes or equipment, including sensitive pressure gauges, pressure transmitters, and diaphragm seals.
That said, the concentration of fluoride typically added to drinking water is so low that there is minimal risk of corrosion of piping or equipment.
Low Concentrations of Fluoride in Water Do Not Cause Corrosion
The Centers for Disease Control and Prevention notes that at the level of 0.7 to 1.2 parts per million recommended by the U.S. Public Health Service for fluoride in public water supplies, the fluoride ion has little to no ability to cause corrosion.
According to the American Water Works Association Research Foundation, “the corrosive influence of fluoride in drinking water is not significant compared with other ionic influences [especially chlorides].”
Moreover, the CDC highlights that fluoridating the water supply using fluorosilicates contributes to improved water stability with reduced overall potential for corrosion because the silicates settle on and stabilize the internal pipe surface.
Of note, adding fluorosilicates to high-purity groundwater with little natural buffering can, however, lead to a slight increase in corrosion.
Special Hybrid Alloys Are Resistant to Fluoride
Some areas, however, have naturally high fluoride levels in the groundwater. This can lead to the local water utility having to treat the water with reverse osmosis or other methods to make the water potable.
If you are dealing with naturally high fluoride levels in local water or you have manufacturing or refining processes that involve media containing fluoride, you will need a diaphragm seal made of a special fluoride-corrosion-resistant material to protect your sensitive measuring instruments.
The engineers at WIKA can work with your team to recommend seals made from or coated with special hybrid alloys designed to resist fluoride corrosion. The WIKA team also points to research that shows hybrid alloys with high molybdenum and low chromium content offer superior resistance to fluoride-containing environments, especially high-temperature fluoride environments. While the WIKA Diaphragm Seal team of experts can offer advice and information on the type of material to use, the customer has the ultimate final word on the decision.
If fluoride corrosion is a problem at your facility or if you’ve got any questions about measuring instruments, give the experts at WIKA a call and we’ll get you on the right track.