mmmatt:
Hi I'm having a relatively common problem with a water sensor, it's corroding. The pin (+voltage) to the sensor is only turned on for 10 millis once a day but after a month (only 30 sensor readings) it's already corroding. Looks like there's about 0.02 V across the pin to ground.
I'm guessing that the constant low voltage to the sensor is causing slow corrosion.Is there any way to complete block power that's less than 1V, but allow anything over 3V?
those arent hard numbers, just examples of what might work. Hoping there's a simple hardward solution to this, but open to suggestions.
Appreciate any advice and help
(attached is a pic of the corrosion. Not failing yet but it will soon)
Part of your corrosion problem may be caused as you described. But another reason is your sensor has at least two different metals in the water. This will cause an electric current to be generated and will destroy one of the metals over time. Remember your chemistry!
Some have suggested using other metals, all alloys, which doesn't solve the problem. An alloy in water will produce a voltage between the atoms of each metal in the alloy and eventually one metal will be destroyed. Stainless steel takes a while longer, but it will eventually have one of the metal components eaten away. Personal experience.
The ONLY solution is to have PURE metal electrodes. Both of the same metal. Remember in chemistry class, the use of platinum wires in experiments using electricity? Pure titanium may also work. But no alloys. Pure copper is easy to find and may work for you. Find it in soft copper tubing at a hardware store.
Paul