Replacement anodes for hotwater systems

[Rustseeker]

We have noted in your forum a number of members discussing the selection of anodes for their hotwater units.

Being a Anode manufacturer we would like to correct some misunderstandings.

All hotwater systems that are manufactured using steel shells and coated on the internal surface with a glass enamel lining require a anode .

With the expansion and contraction of the steel tank the enamel lining overtime can crack and expose the steel shell, this when the anode becomes active. The anode also protects other disimilar metals inside the tank such as the heating element and the inlet and outlet fittings.

There are two types of anodes used in corrosion protection.

ICCP ( Impressed current cathodic protection)

Galvanic (sacrificial)

In this dicussion we will only cover Galvanic anodes.

Under Australian Standards AS 2239 2003 Galvanic (sacrificial ) anodes for cathodic protection there is 3 anode groups.

Zinc alloy anodes

used in marine applications and as earthing anodes

Aluminium alloy anodes

Mainly used in clean seawater and general marine use , with the exception of a special chemisty for use in

potable (drinking water)

Magnesium alloy anodes

Generally used in freshwater(drinking water) and soils.

The Aluminium anode for use in drinking water is made from high purity Aluminium and alloyed to a specfic chemistry, usually produced in extruded rod form in a diameter of 17 mm , fitted with threaded steel plug.

The Australian manufactured Aluminium anodes have the top of the steel plug colour coded blue for ease of identification.

This anode application is mainly used in areas of "hard "water , high in total disolved solids, where the TDS is in the range of 600-2500 mg/litre.

The Magnesium alloy anodes that are used for the protection of hotwater systems are produced in two specifications.

There application for drinking water is as follows.

1. M1 used in areas of high purity drinking water ie Alpine.TDS levels 0-40 mg/Litre

The Australian manufactured assy is usually 21 mm dia rod. The top of the steel plug is colour code Green for identification.

Note very few of the M1 type is sold or used for general hotwater systems

2. M2 the main anode chemistry for use in hotwater systems.

For use where the TDS levels are 40-600 mg/Litre.

The Australian manufactured assy is usually 21 mm dia (can be 26 mm dia for larger domestic and industrial systems) The top of the steel plug is colour coded Black or Orange .

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