EXPERT TIP #1: WEIGHT & LENGTH OF MAGNESIUM ANODE AFFECTS CP SYSTEM LIFE & PERFORMANCE

EXPERT TIP #1: WEIGHT & LENGTH OF MAGNESIUM ANODE AFFECTS CP SYSTEM LIFE & PERFORMANCE

Magnesium Anode Current Output & Service Life

Key Facts:

• Longer anodes produce more current than shorter anodes.
• Doubling the diameter of the anode will increase the volume (weight) by a factor of 4; yet, will only increase the current output approximately 15%.
• Greater anode weight (volume) increases the anode or system life.
• Surface area of the anode is not as important as some people believe.
• High potential anodes will always generate more current than a standard potential anode given the same resistance-to-earth.

Myths:

Almost a Myth - System life can be calculated by using the published deterioration rate of 17 lbs. per ampere year.  This is a good start but anodes, as they consume, will become physically smaller, therefore producing less current.  For that reason, we always include a "utility factor" when calculating anode life.  If basic calculations require 100 lbs. of anode material, specify a minimum of 130 lbs. of anode material, a 1.3 to 1 utility factor. 

Full Myth - Installing two anodes will double the current output.  Not true. In most instances, it will be less than double.  The distance between the anodes will effect how much total DC current the system can provide.  The farther apart the anodes are spaced from each other, the better.

The chart demonstrates the effect of various physical anode sizes to current output & service life.

Example 1:

1" X 60" anode can generate 0.139 amps

2" X 30" anode can generate 0.095 amps

Note: The 1" anode is half the weight and twice the length of the 2” anode yet they have identical surface areas.

Example 2:

1" X 60" anode can generate 0.139 amps

4" X 30" anode can generate 0.117 amps