environmental concern with anode bedding

ONENGINEER · Oct 27, 2015

The anode bedding cast iron/coke breeze runs along the road adjacent but not within a site. It is for corrosion protection of a gas pipeline.

Is there generally any environmental concerns due to the presence of anode bedding for the site nearby. The ground water is within 1 m of the surface and the soil is composed of silt and sand. Thank you.

bimr · Oct 27, 2015

In cathodic protection, a metal anode that is more reactive to the corrosive environment of the system to be protected is electrically linked to the protected system, and partially corrodes or dissolves, which protects the metal of the system it is connected to.

Zinc is a common anode material and is not considered to be hazardous, but zinc is a water pollutant. Coke is a fuel with few impurities and a high carbon content, usually made from coal. It is the solid carbonaceous material derived from destructive distillation of low-ash, low-sulfur bituminous coal.

Water moves very slowly through the soil so zinc should not be an issue. However, it would be prudent not to install the anodes close to a shallow well or in a wellhead protection zone.

SlideRuleEra · Oct 27, 2015

Assuming this is coal coke breeze (not petroleum coke breeze), the only known concern is fugitive dust. Since the coke breeze is being used for in-ground anode bedding, I doubt that is a problem.

Pipelines are usually protected with an impressed current cathodic system with an independent DC power source. Anodes for impressed current systems are typically inert, such as silicon iron, and are not physically connected to or even very close to the cathode (gas pipeline).

Electrical conductivity at the anode field is improved with proper bedding - like coke breeze. So much so, be sure the impressed DC current density is properly set and maintained. Otherwise, anode life will be shortened and metals such as aluminum, lead, or high-strength steel near the cathode (gas pipeline) can be damaged.

Reactive metals, like zinc, are sacrificial anodes for passive (galvanic) protection of structures that are more compact than a pipeline.

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