Road salt accelerates the breakdown of anticorrosion agents and touch-up paint, while paint applied under works conditions is only affected by road salt to a small extent. Salting causes corrosion to start earlier and also increases its rate.
In tests on unsalted roads several effects were valued in monetary terms in order to assess the advantages and drawbacks of salting. Through discussions with experts, the conclusion was drawn that the life of vehicles would be increased by 25% if application of salt were to cease. The cost of corrosion due to winter salting in 1985 was estimated at SEK 1.7 billion, i.e. SEK 0.12 per vehicle km.
Investigations also indicate how corrosion resistance has changed over the years. It seems that corrosion resistance improved during the 1980s and up to the middle of the 1990s, but that corrosion resistance since then has been about the same, as shown when some vehicles from each year model and after some years in use, were examined.
If we assume that the total improvement from 1985 to 2005 is 20%, we find that the cost per vehicle km is just under SEK 0.10. If this is multiplied by 1.8, i.e. the retail price index for this period, we have a cost of SEK 0.175 per vehicle km. The total number of vehicle km is 72 billion per year, of which 35% is carried out during the winter (5 months). If we also include those who drive on salted roads only occasionally, we have that 90% of the winter vehicle mileage is affected by salt, i.e. 72 x 0.35 x 0.90 x 0.175, which gives the cost of the corrosion of bodywork due to winter salting as about SEK 4 billion per winter, i.e. about SEK 1000 per vehicle annually.
Corrosion of electronics is considered to be the next great corrosion problem. Electronic equipment is often used to control other technical equipment in e.g. vehicles. Stringent demands must therefore be specified for the reliability of electronics. Even now it is usual for electronics to be installed in vehicles, and in future this will be increasingly common. The environment on roads and streets is heavily polluted and chemically very aggressive. This makes corrosion a very difficult problem.
The problem with encapsulation of electronics is that most encapsulation materials let in moisture in some way, which gives rise to corrosion. Salt can be kept out by encapsulation, but moisture is more difficult. Since salt gives rise to a moist environment, it is likely that it causes increased corrosion, but this must obviously be investigated.
Two scenarios, based on rough assumptions, can be envisaged. One is to assume that salt has no effect at all, and the other that it gives rise to the same cost as the corrosion of bodywork, i.e. SEK 0–4 billion. If the mean of this is used in calculations, we arrive at SEK 500 per vehicle annually, i.e. SEK 0.0875 per vehicle km.
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- Research area: Vehicle technology, Infrastructure maintenance
- Published: 2006-10-31
- VTI-code: N24-2006
N24-2006 (34 pages + 1 Appendix including 1 page, 270 kB, written in Swedish with an English summary)
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