The requirement for matrix metal is resistance to electrochemical corrosion, mechanical strength, easy to manufacture, the surface is easy to form passivation film and good electrical conductivity.

Electrode matrix can use any conductive material, such as iron, nickel, lead, copper and other metals and their alloys, but also with Chromium, magnesium high-Silicon iron. But preferably valve type or membrane metal.

The valve type metal is conductive when used as a cathode by saline electrolysis, but is not conductive when used as an anode and has the property of a one-way load. Valve metals include titanium, niobium, tantalum, zirconium, tungsten, aluminum, or alloys of two or more of the above metals. The electrode matrix is usually titanium and, in exceptional cases, tantalum and niobium.

Titanium, tantalum and niobium produce a strong film of passivation when anodized. In the presence of chloride ions, titanium will cause severe corrosion.

When the external voltage is below 10V, the reactions of the three metals are almost identical, but over 10V, the current of titanium is dense

When the external voltage is below 10V, the reaction of the three metals is almost the same, but over 10V, the current density of titanium can be seen to increase, which is the result of local corrosion of titanium. Tantalum and niobium showed strong corrosion resistance even in the polarization of the external voltage above 10 V. Compared with tantalum and niobium, titanium has the advantages of being cheap and low density, so the relative price per unit volume is about 1/20 of tantalum and 1/10 of niobium. But titanium has 3 to 4 times the resistivity of tantalum and Ni and 25 times that of copper, and being used as an electrode structure material is a drawback.

The passivation properties of anode matrix metals are expressed by the destruction potential(Ec) and the protection potential(Ep).