Corrosion testing laboratory of Technopark Kralupy scored high in round robin tests
Corrosion testing laboratory of Technopark Kralupy participated in two round robin studies of accelerated corrosion tests.
The first one was organized by Bekaert from 2018. It was looking at reproducibility of the neutral salt spray test, NSST, according to the EN ISO 9227 standard. This widely used accelerated corrosion test is often criticized because of a significant spread of results between particular laboratories. It is linked to variations in preparation of sodium chloride solution (concentration, pH and presence of traces of heavy elements), temperature and absolute amount and uniformity of salt fog deposition over the sample surface. Indeed, there are procedures to limit such undesirable effects defined in the standard. However, practical experience proves that there are testing laboratories providing flawed test results due to incompetency, attempts to make customer happy by making test conditions less strict, or cost savings.
In the Bekaert round robin test, 10 laboratories from all over the world were following the time to red rust formation for identical steel wires coated with zinc and zinc-based alloys. Exposure of the coated steel wires to salt spray took up to 6000 hours. Results obtained in several testing labs differed strongly from mean values, see error bars in the chart in Fig. 1. Further analysis identified varying salt spray deposition and incorrect composition of sodium chloride solutions as the main sources of the deviations. Corrosion testing laboratory of Technopark Kralupy belongs to the laboratories with most consistent results closest to the mean values. For example, the mass loss of reference zinc coupons corresponded exactly to the mean value defined by the standard, i.e. 50 g/m² in 48 hours.
Fig. 1. Results of round robin test of NSST organized by Bekaert: time to 5% coverage of coated wires with red rust
The second round robin study focused on performance of carbon steel coupons under conditions of the cyclic accelerated corrosion test Nissan CCT1. It was organized by the Czech headquarters of Bosch in 2020. Corrosion testing laboratory of Technopark Kralupy ranked again very well with the lowest deviation from the mean corrosion loss of the tested coupons.
Both studies proved that corrosion tests performed in Technopark Kralupy are executed with maximal care and provide correct and trustable results. Details on corrosion testing services of our laboratory are available here.
