Conventional sacrificial anode systems
Conventional systems are fitted to industrial structures such as pipelines, underground tanks, above ground tanks and many other steel structures cited on or in the ground. It is normal to provide them with corrosion prevention (Cathodic Protection – CP) by attaching a number of metal blocks (Anodes) of very active metals such as magnesium to the steel structures. This process results in the more active metal (magnesium) then corroding away and generating a small amount of cathodic protection DC current.
A typical magnesium sacrificial anode System has a life expectancy of ten years. The typical anode bed comprises of five or more anodes and will have a primary cost of AUD $1250.00. The installation and commissioning costs of that anode bed including civil works and commissioning would typically be AUD $2,000.00.
Cost regarding replacement Systems
Because many sacrificial anode systems are installed on pipelines often in congested city streets in urban development, the costs to excavate and install new anodes on a ten-year cycle can result in replacement costs as much as $10,000.00 per site per 10 years. With such installations being installed every two to three kilometres along a pipeline route, the accumulated replacement costs over a fifty-year life cycle of a pipeline can be in the hundreds of thousands of dollars.
The CO2 Footprint
The production of one kg of magnesium generates a CO2 Footprint of 42 kg of CO2. The annual average magnesium tonnage per annum utilised by the cathodic protection industry in Australia alone is in excess of 400 tonnes. This equates to an annual CO2 footprint of 16,800 tonnes of CO2. At a cost for CO2 at $23.00 per tonne, this equates to an annual cost to industry before materials of $386,400.00.