Anti-corrosion techniques could double the life of steel

The techniques, which could reduce steel corrosion rates by 50 per cent, involve passing an electric current through a material or applying an electromagnetic field to a material for two to three minutes.

Andreas Chrysanthou, leader of the Materials Research group at Hertfordshire University, said: ‘The work so far is showing that there is some kind of reduction in the residual stresses.’

These stresses form in a material and create defects, which alter the electrochemical behaviour of a material from one side to the other.

‘Through using these new techniques we’re hoping to produce a more uniform structure by manipulating the composition of the material at a microstructure level,’ said Chrysanthou. ‘Our research suggests this will then reduce the corrosion levels.’ 

The team has so far completed seven experiments but only one of these has been conducted using the electromagnetic field technique. However, Chrysanthou claims that the end result is the same for both techniques.

Douglas Michaels, technical secretary from the Institute of Corrosion, said: ‘The problem I have is seeing how the electromagnetic field mechanism will work. There is nothing inherently obvious about how very strong electromagnetic fields will affect the structure of the steel.

‘It is possible that they induce some heating effect, which grows the air-formed oxide. This might cause the oxide film to take longer to break down. However, this would not be a lasting effect.’

Chrysanthou countered this by stating the work done so far suggests the techniques have an affect on the dislocation density — effectively reducing the residual stresses on the material and these are the same stresses that can actually lead to more corrosion.

’It’s early days yet but this is what we suspect at the moment. I have some scepticism about it myself,’ said Chrysanthou. ‘We are doing the work at the moment to better understand the mechanisms.’

The tests so far have been on sheet material mainly varying from 0.8mm to 1.5mm in thickness, with one of the experiments being done on a cylindrical bar with a diameter of 10mm.

Chrysanthou said the team would be inviting industry to seminars with the aim of getting them to invest in the technologies and fit their own rigs.

The Institute of Corrosion claims that it costs the UK 3–4% of the GNP each year, which equates to about £30–40bn.

A recent grant of €278,680 from Marie Curie International Incoming Fellowship has been awarded to the project and will be put towards carrying out further research.