Road salting in the wash

  • Getting cars clean in variable winter conditions is a challenge. Many blame road salting for this. Why, and is there any truth to the claim?
  • Tekno-Forest Oy's test team investigated the issue in an article published in Petrol News in 2018.

Is road salting the cause of winter washing problems?

The study examined the washing performance of washing machines in three different stations in the same service chain. Six clean test plates with a painted surface were fixed behind the front tyre of the car, close to the skirting. The car was then driven along the freshly salted Helsinki-Tampere motorway until a uniform and sufficiently thick layer of dirt accumulated on the surface of the plates.

After the discs were removed, three of them were left outside in the shelter. The other three were moved indoors for two days to dry. In this way, both plates coated with fresh dirt and plates coated with stuck dirt were included in the test.

In addition to these test plates, three clean test plates were coated with asphalt bitumen film in the laboratory. The film was allowed to dry on the surface of the plate for two days. The set of three plates (fresh, stacked and coated with bitumen film) was then attached to the car's siding and the car was driven to the test wash at all three stations.

For each washing machine, the most expensive "Brilliant Wash" programme was selected. The programme included a separately applied pearl solvent. This ensured that the test plates were washed using a strong pre-wash detergent.

  • The test washes were carried out on the same day, within three hours. The outside temperature was -1 C.
  • The test sheets were photographed just before entering the washing machine and immediately after the wash cycle.

What did you find out in the washes?

In all three washes, the salt stains almost completely disappeared from the surface of the test plates. Some dark spots (bitumen spots) remained on the test plates of the first and third test stations.

The clearest difference was in the washing of the brown bitumen film. At the second test station the slab was mostly cleaned, whereas at the first station only slight cleaning was observed. At the third station, the bitumen film had almost completely remained on the surface of the plate.

The best washing result for stuck brine was also achieved at the second station. At stations one and three, the salt dirt had hardly been cleaned off the surface of the test plate at all.

The right detergent for challenging conditions

  • The test results confirm that there are large variations in the quality of washing results between stations in the same chain. Station two achieved an acceptable washing result, while the poor results of stations one and three indicate the use of a detergent system unsuitable for winter conditions.


  • The variation in the quality of washing programmes of the same name is explained by the use of washing machines and chemicals supplied by different manufacturers within the same service or washing chain.


  • The poor wash performance of stations one and three is also partly explained by the lack of winter settings in the wash programmes or by the fact that the pre-solvent levels in the programme were left too low.


  • It is also possible that the "euro/ wash" contract applied in the sector is the reason for the general collapse in the quality of washing in winter conditions. Fixed price contracts, independent of the washing programme, do not encourage chemical suppliers to adjust detergent concentrations to the level required by the conditions, as this will increase costs proportionally. This in turn increases the risk of increasing customer dissatisfaction with the washing performance of the station, which in turn leads to poor wash sales and increased demand for hand-washing services.

To prevent this from happening, the right type of solvent detergent, targeted at the right place, at the right concentration and with the right duration of action, is needed for the most challenging winter conditions.


Source: petrol news 1/2018