Zinc Anodes for Soil Application by Farwest Corrosion

Background on Zinc Anodes

An industry standard for many years, zinc galvanic anodes are utilized to protect a variety of steel structures from the affects of corrosion. Historically, zinc anodes have been designed for use in salt or brackish water applications. Due to the U.S. Navy’s widespread use of zinc in the early 1950’s, a specification (MIL-A-18001) was developed for galvanic zinc anodes in seawater. This zinc specification, with revisions, is still in use today and is a standard in the corrosion control industry.

Soil Anodes

Farwest provides sacrificial zinc anodes made to ASTM-B-418 Type II specifications for corrosion protection of steel structures in soil. These anodes are made from 99.99% pure Special High Grade Zinc and are ideally suited for galvanic protection of metal in soil.

• Fabrication – Farwest attaches an insulated copper lead wire to the anode core Zinc Anode and seals the connection interface with heat shrink tubing or with layers of suitable splicing tapes. The wire size, length and insulation type is typically chosen by the customer depending on the application. If required, Farwest also packages the anode in a cloth bag filled with a low resistance backfill mixture consisting of 75% hydrated gypsum, 20% Bentonite and 5% sodium sulfate.
   
• Applications – Due to the fact that zinc anodes have a lower driving voltage than that of magnesium, zinc anodes are typically used in low soil resistivity applications. Typical applications include buried pipelines, tanks and a number of other similar uses.
   
• Available Sizes – Zinc soil anodes are offered in a variety of sizes shown on the chart below.
   
• Anode Cores – Zinc soil anodes are normally cast with a ¼” galvanized mild steel core to which the anode cable is connected.
   
• Installation Methods – Zinc soil anodes can be vertically or horizontally installed in native soils and should be wetted before burial. The anode cable can either be connected directly to the structure or through a cathodic protection test station. Typical cable-to-structure connection methods include welding and mechanical attachment.