Protect Sensor From Saline Water

304 is reasonably good for corrosion resistance in contact with sodium chloride, according to this, so it might not be a worry if only AC is being used to make the measurement.

If DC is being used instead, the 304 being + might give rise to its corrosion, and the 304 being - might lead to its becoming plated, depending on what else is in the water other than sodium chloride. If nothing else is present, then there might be some off-gassing of hydrogen in the case of its being - and chlorine in the case of its being +, which needs to be allowed for in the ventilation arrangements for the equipment and wherever it is being mounted.

What is the other electrode made of, incidentally?

AISI 304 is not a good material selection if the chloride content is above approx 200 ppm-500 ppm, another factor you have to consider is the operating temperature.

would consider to change the material to a more resistant is saline water like duplex.

Vitt

corrosion & rust protection

Endress + Hauser (usual disclaimer) do a range of conductivity-based level probes that have carbon-loaded PTFE as the wetted electrode material.

Thanks. Can you please suggest any vendor who can do PTFE coating on my sensors. The temperature limit is 90°C

Madhukar,

Your previous thread indicates you are in India. A quick Google search brought me to Tuff Fab, a vendor which appears able to meet your needs. They are located in Chennai, Tamil Nadu, India.

Regards,

Tony

get the sensor plastic coated

http://www.google.co.uk/search?q=plastic+coating+dip&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-GB:official&client=firefox-a

If the sensor is a capacitance-based one, rather than a conductivity-based one as earlier replies appear to have assumed, then the metal itself doesn't need to be wetted by the saline water, in which case peterg7lyq is correct as above - it can be plastic coated. However, if it is a conductivity-based sensor, an electrical connection between the electrode will ordinarily be needed, which means that plastic coating cannot be expected ordinarily to work, although there are conductivity sensors that can operate in high-conductivity fluids that are fully plastic-encapsulated. What level is the salinity?

So the method of measurement, which hasn't been stated in the original post, is fundamental to adequately answering the question over what to do with the electrode(s).