Stainless steel electrodes act as battery?

[Windzero]

I have two probes. They consist of a stainless steel cylinder inside another, one held by epoxy and one held by acrylic. I can measure a voltage difference between them. I have placed them in tap water and applied a 5V difference across them then disconnected the voltage. The problem is that they act as a battery and hold a charge and then slowly dissipate the charge. I can understand this happening if the two cylinders were made of different metals, but they are the same. Any help would be greatly appreciated.

 

[Drakkith]

I'm assuming that you mean they act like a capacitor? A battery produces voltage through a chemical reaction. It sounds like your cylinders are merely holding a charge between them like a capacitor.

 

[Dr_Morbius]

If there is any difference in the composition of the 2 steel cylinders you will see a voltage generated. If there is a difference in the oxide coatings of the cylinders you will see a voltage generated. Stainless steel is protected by a thin oxide layer. Also if there is a difference in the composition of the materials that the cylinders are in contact with you will see a voltage generated. Basically unless the cylinders are exactly alike and in contact with materials that are exactly alike you will see a voltage generated. You might even be generating a voltage from the probes coming in contact with the cylinders either chemically or through thermoelectric processes.

Just because they're made out of stainless steel doesn't mean they can't participate in chemical reactions.