Car warranty fears over council road gritting technique

01 October 2008

The level of warranty claims on vehicles could rise ‘dramatically’ over the next decade, as a result of corrosion caused by a widely-used pre-wet gritting technique.

Research by car manufacturer Volkswagen has shown that liability cases against its cars in Austria, where pre-wetting is common, have risen by more than 60% in three years.

Recent testing by German manufacturer Volkswagen, which involved metal plates being attached to gritting lorries, has also shown ‘significant’ corrosion to vehicles operating in pre-wet conditions.

Dr Jorg Struve, of the Central Laboratory of Metals and Surface Technology, at Volkswagen, said: ‘I have no doubt that the pre-wetting technique has led to increased corrosion to vehicles, and it is inevitable we will see the same happen in the UK in the next decade.’

Many local authorities in the UK favour the pre-wet option and it has also been adopted by the Highways Agency. The agency is planning to roll out use of the treatment across most of the UK motorway network in the next three years.

Pre-wetting involves applying around 30% of saturated sodium chloride brine to dry salt. A holding tank on the gritting vehicle discharges the brine via spray method as the salt leaves a spinner mounted on the bottom.

It is considered by many local authorities as the most effective way of applying salt to the road network.

Professor Tony Hindle, senior lecturer in operational research at Lancaster University, told Surveyor: ‘The suggestion that corrosion costs are a thing of the past for vehicle manufacturers is very wrong. The growing body of evidence that suggests pre-wetting leads to increased corrosion is a big worry.’

Brian Smith, president of the County Surveyors’ Society (CSS) and deputy chief executive of Cambridgeshire County Council, said his own council had moved towards pre-wet in recent years in rural areas, and would be ‘reviewing our position’.

‘I am sure that managers involved in decisions about winter maintenance will want to fully understand the findings and consider the relevance and cost issues for their own operation,’ he added. The Road Haulage Association (RHA) told Surveyor that it was ‘concerned’ about the situation and ‘would monitor developments carefully as regards to corrosion on behalf of its members.’

One supplier of gritting lorries revealed that chassis’ lives were being reduced by between two and three years because of corrosion.

‘And these are chassis’ of well-known manufacturers as well,’ a source told Localgov.co.uk sister title Surveyor.

But defending pre-wet, an HA spokeswoman said: ‘The decision to use pre-wet is based on a substantial amount of ongoing research and evidence from across Europe. Pre-wet uses less salt on the network, which has to be better for everyone.’

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