Tungsten (W) is the main raw materials of tungsten points, that is to say, analysis of tungsten points’ surface film from its electrode potential is similar to the analysis of tungsten.
Each species owns the characteristic of standard electrode potential, which is a kind of equilibrium electrode potential.
The standard electrode potential at 25 ℃
Metal | Ion | Electrode potential (V) |
W | W | -0.2 |
Ni2+ | -0.23 | |
Ag | Ag+ | +0.799 |
Cu | Cu2+ | +0.34 |
Pb | Pb2+ | -0.126 |
Fe | Fe2+ | -0.44 |
Standard electrode potential---put a matter in some kind of solution, which contains matter’s ions, the potential difference between the matter and the standard hydrogen electrode is the very standard electrode potential when ion concentration is 1g / L. The metal will be more active when negative value of standard electrode potential is bigger; but it will be less active when standard electrode positive value is larger.
What can be drawn from the table is that the potential difference between W and Cu is the biggest, which is 0.54V. The points’ material electrochemical corrosion is prone to appear in a high temperature, high humidity environment. Nevertheless the corrosion between W - Ni is slighter than W - Cu’s, W – Ag’s. Electrochemical corrosion is not prone to occur since the potential difference of W - Ni is only 0.03V, whose. Therefore, adding a right amount of Ni can improve oxidation resistance property of tungsten points, which will reduce the formation of its surface film.
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