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PTFE for solenoid valve actuators?

2002

We are trying to use a small 1/8" NPT Solenoid valve for a marine aquarium application. The 304 SS plunger and spring are not satisfactory as they do rust over time. Some of the solution in contact with the valve is saturated salt.

Can we satisfactorily use a PTFE coating for the plunger and spring? Would this add significantly to the life expectancy? Would additional Nickel coating also help? What additional OD is added by the PTFE (and Nickel)?

ny suggestions would be appreciated.

John S Krum
- Leicester, North Carolina

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2002

I doubt if the solenoid plunger and spring are stainless steel. SS304 is not suitable for the plunger because it does not have the appropriate magnetic properties and SS304 is poor spring material.

Teflon is unlikely to work well for the plunger as at the end of the stroke a plunger has to impact some kind of stop and this would damage the teflon quite quickly.

I think you would be better advised to find a truly corrosion resistant device rather than fix up the one you have got. It would probably be cheaper.

Good luck,

John Holroyd
- Elkhorn, Wisconsin

John Holroyd suggested that the customer go to another source! I agree l00%. And what J.H. said about teflon sounds l00% correct. It will deform under load and lose its seal ...

John Krum didn't say what type of solenoid valve he had. On/off? Control? But I bet he has a multi-ring labyrinth type seal and NOT a diaphragm ... which is far better where salts are concerned!

Hence it sure sounds as if he has the wrong design for salts.

Freeman Newton [deceased]
(It is our sad duty to advise that Freeman passed away
April 21, 2012. R.I.P. old friend).
2002

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A high phosphorous electroless nickel teflon codeposition or high phosphorous electroless nickel may solve your problems.It may be necessary to plate up to .002in thickness. I would start with .0002in for the teflon codeposit and .0005 in. with the high phos.. Todd Osmolski - Charlotte, North Carolina, USA 2002 2002 John Krum is experiencing corrosion of the solenoid core spring and most likely the shading coil, if an A/C coil, due to incompatibility with the media. This is a common problem with "wetted core" solenoid valve designs. What John needs to investigate is a "shielded Core" solenoid valve. This design has a diaphragm mounted in between the solenoid and the valve. This isolates the metallic components from the media. Application of a shielded core valve requires the following: 1.Media and concentration and temperature for material selection. 2.Inlet and outlet (downstream) pressure. 3.Flow rate 4.Voltage. The outlet pressure is very important as the core spring is now entirely responsible for closing the valve. These types of designs usually have a maximum allowable back pressure value. If exceeded the valve will not close or stay closed. I hope this helps... Anders Ryan valve company - Cedar Grove, New Jersey