Single-electrode method applies testing principle of half-cell self -potential method, the rebar under ionic environment
can be seen as an electrode, after corrosion, electrode potential change, therefore, potential reflects corrosion directly.
As it is well-know, battery consists of cathode and anode, Since rebar electrode has only half feature of the battery,
therefore it is called half-cell.
Double-electrode method also applies self-potential method. The difference only lies in that single-electrode method
applies to outside exposed structure of rebar end, while double-electrode method aplies to non-outside structure.