Soils That Eat Metal

Our fenced reserve is constantly under threat. Every night, cats and rabbits patrol the outside of the predator-proof fence looking for weaknesses. And unfortunately, the region’s soils work against us, constantly eating the steel in the fence as what must be some of the most corrosive soils in Australia.
A feral cat attempts to climb the predator-proof floppy top fence at Arid Recovery

This has been huge problem for Arid Recovery. Wire that we place in contact with the ground to form a ‘skirt’ or ‘apron’ to prevent digging animals may only last 5-10 years until it corrodes enough for animals to dig through it. Pegs to hold down wire come out rusted to sharpened points after less than 6 months in the ground. On occasions where feral animals have managed to dig into the reserve, there have been weeks to months of stress and effort in trying to remove them. To keep ahead of the rust, every few years we need to order truckloads of new netting wire and organise big teams to roll the new wire out over the old corroded sections. This is a lot of work and very costly.

Steel pegs rusted to points after less than 6 months in the ground

We’re not alone in having infrastructure threatened by corrosion. This region is regarded as the worst area for rust affecting the 5,500 km dog fence, and mining and municipal infrastructure face similar issues.

We needed a solution. So a chance encounter with a soil science student at Adelaide Uni proved to be the opportunity to get to the heart of the issue. Enter Andrea Stiglingh. Andrea had just completed her Honours research and was interested in conservation of Australian animals. She jumped at the opportunity to work on the project and from there we developed a crack team.

Andrea’s work on soil corrosion properties is supported by soil scientist Prof. Rob Fitzpatrick of the University of Adelaide’s Acid Sulfate Soils Centre, Luke Mosely, Ron Smernik and colleagues. Metallurgists, engineers and product innovators joined the team from Waratah Fencing Products – Robert Fabien, Warwick Andrews, Bradley Taylor, Geoff Smith and colleagues. Waratah also very generously sponsored much of the research costs.

Project team at Arid Recovery

Now, our research has begun in earnest. The soils around the reserve have been mapped and compared to the extent of fence corrosion at each point. Hundreds of soil samples have been taken back to the lab and measured for physical and chemical properties. The team have used X-ray diffraction to analyse the chemical makeup of samples of rusted fence.

And this is where specialists from Waratah come in. Metallurgists have produced samples of standard netting products, and produced new products to be tested in the soils around Arid Recovery. Tests are also being run in nifty accelerated corrosion setups in the lab. This June, the project team gathered at Arid Recovery to bury the netting samples into the ground. We placed a range of coated steel products in the soil. There’s nothing like all getting on the end of a shovel and digging dirt for some team bonding!

Laying netting samples into experimental plots

We’ll periodically return to our plots to check on the rate of corrosion of the different samples, starting at the 6 month interval. Hopefully, our results will come up with a good solution for the most cost-effective fence maintenance in the long-term, and so our money set aside for replacing wire every few years can be used to instead control feral animals and continue returning native wildlife to the desert.

With more conservation fencing (or safe havens) being constructed and planned around the country, we hope that our results will be useful for others in developing the best fence design and ongoing maintenance strategies, giving our wonderful natives a safe home for many years to come.