The standard "DIN 55635 Paints and varnishes - Cyclic corrosion testing of coating systems on materials and components in automotive construction", developed by the German Institute for Standardization (DIN), describes an accelerated test procedure for evaluating the corrosion behavior of materials and components used in automotive construction and the corrosion protection provided by coating systems. This test method is based on real corrosive conditions and provides different results for a wide range of uses in automotive applications.
When performing the test, test samples are placed in a closed chamber and positioned at an angle of 65 degrees to 75 degrees from the horizontal, with the side to be tested higher. The salt spray stage is performed with a 1 percent sodium chloride solution (pH between 6,5 and 7,2) and sprayed onto the samples at a rate of 2,0 to 4,0 ml/80cm² per hour.
A complete test cycle takes 7 days. Cycles A, B, and C are multi-step cycles consisting of temperatures ranging from 15 degrees to 50 degrees and humidity ranging from 50 percent to 95 percent. Typical test duration is six complete test cycles (6 weeks).
This corrosion test incorporates significant experience from the automotive industry to obtain as realistic and timely a result as possible. An important element of the test is therefore a low temperature phase followed by a phase with high relative humidity.
A shortcoming of many corrosion tests is that corrosion is exaggerated by excessive salt loading. Studies of snow water on roads after road salt application have reduced the previously usual 5 percent to 1 percent, leading to a more practical salt concentration in this test. This climate change test takes into account the possible passivation of surfaces under outdoor conditions at humidity levels between 60 and 80 percent by means of humidity and temperature control.
The test method described in this standard is based on real corrosive climatic conditions (i.e. temperature and humidity cycles).
The alternative test consists of three different 24-hour cycles based on different real load scenarios and combined in a fixed order:
The cycle order is as follows: BACABB A. The duration of the test cycle is 1 week. The typical test duration is 6 test cycles (6 weeks).
After the tests, the samples are subjected to the following processes: leaching, filamentary corrosion on aluminum and steel, blistering, rust level and liability.
With cyclic corrosion testing, corrosion phenomena can be generated on modern substrate materials such as aluminium, galvanized steel or galvanized steel with zinc-magnesium alloys, in a way that is well adapted to the external weather conditions and in significantly shortened times. Due to the great importance of new metal surfaces in the automotive sector, this topic was taken up by the VDA working group with the aim of developing a reliable and accelerated corrosion test that evaluates these materials in a practical application.
Among the numerous tests, measurements, analyses and evaluation studies that our organization has carried out for businesses in various sectors, it also provides testing services defined in the standard “DIN 55635 Paints and varnishes - Cyclic corrosion testing of coating systems on materials and components in automotive construction” with its trained and expert staff and advanced technological equipment.
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