How does electrochemical corrosion protection on «Antonio Merloni» gas tanks function? (part 1)

(pic. 141.1 - How electrochemical
corrosion functions)

Electrochemical metal corrosion protection under the ground is provided by sacrificial anode. But how does it function? Which components does it consist of? Let’s consider this point and study three - component protection included in Italian gas tanks from «Antonio Merloni» «with the microscope».

Gas cistern (subject to be protected) produced of low-alloyed steel is connected to negative pole of external current supply source what creates cathodic polarization. Application of electronegative potential will provide protective action: it will reduce self-dilution speed (destruction) for the metal up to touch bottom value allowed by operating conditions. Cathodic process runs on entire the surface of the cistern where all the points have equal potential while anode process (which provides corrosion) shifts to sacrificial anodes connected to «plus».

In other words, the protection prevents steel (or any other material) corrosion inside this environment. Consumable anodes protect metal giving it their energy and accepting damaging effect.

Current in the following circuital: «positive pole – anodes – corrosion environment (sub-soil) - gas tank – negative pole» is protective current. The quality of protection is characterized by electrolytic potential of the cistern – protective potential.

Copper/copper sulphate electrode (Cu/CuSO4) has high corrosion resistance. Electrode positioning in the ground: 30 cm from the body of the gas tank, on the datum line - half height of the cistern.

(pic. 141.2  - Electrochemical protection
on «Antonio Merloni» gas tank)

Magnesium anodes placed in textile bags should be completely covered (30 cm from the gas tank, on the datum line of cistern bottom) and connecting cable should be fixed inside the waterproof body.

Waterproof distribution box is designed for electrode and anode cable connection and allows to realize control observation.

Good electrolytic contact is provided by the ground (river sand) where electrode, anodes and protected cistern are placed in. To provide maximum electrical conductivity the ground next to anodes and electrode should be well moistened. Electrical contact is provided by metal conductors.

Electrochemical corrosion protection on «Antonio Merloni»: 1. Grounding; 2. Control unit; 3. Hat; 4. Warning tape; 5. Security rules; 6. Sand; 7. Protective anode; 8. Electrode; 9. Lower lever of the pit

Similar articles:

1. Article «Anode-cathode protection: guarding the gas tank»
2. FAQ «Why should we use electrochemical protection for the cistern?»
3. Video «Gas tank mounting, ground works»

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