Methods & requirements

Scania STD 4445

Corrosion testing determines the resistance of materials to corrosion under specific environmental conditions, like temperature and humidity. Other accelerating factors can be presence of chemicals and the pH-level of the salt fog and pluviometry.

There are mainly two different types of corrosion test standards, field performance and accelerated corrosion tests. Proton Technology is focused on different types of standardized corrosion tests.

What is important when choosing a test method is to make sure the controlled environment matches the natural outside environment in terms of behaviour of the protective coating when it degrades. Since the methods used in a laboratory environment are accelerated, studies must underpin the extrapolation of test duration.

Control Art Chambers used for Scania STD 4319

Accelerated corrosion testing by Scania STD 4445, ACT 2 (Type 2)

The test standard Scania STD 4445 describes a test method called ACT2 which is an abbreviation of accelerated corrosion test, ACT version II, and is a test method used for testing the corrosion resistance on vehicle parts. The standard Scania STD 4445 is based on the Volvo standard VCS 1027,1449 and defines an accelerated corrosion test method to be used in assessing corrosion resistance of metals influenced by chloride ions from salt spray solution. The test is performed by simulating atmospheric corrosion conditions in a controlled way and is used for:

Aluminium and magnesium substrate with organic coatings
Anodised aluminium
Crevice corrosion on surface coated ferrous metal substrates

Test procedure and assessment

Samples to be tested for corrosion resistance according to Scania STD 4445, are tested in controlled climate chambers during a defined exposure time. The exposure time in the chamber is described by requirement standards and requirement level and depends amongst other on the surface treatment of the test samples.

The accelerated corrosion test is finished when the specified exposure time for the test samples is reached. Upon finishing the corrosion testing the samples are evaluated for corrosion resistance. Several assessments are applicable: general corrosion, propagation from scribe and evaluation of edge corrosion.

Test cycle

During a corrosion resistance test according to Scania STD 4445 the atmospheric corrosion conditions are accelerated using a cyclic corrosion test method in a controlled chamber.

The test cycles consist of controlled humidity and temperature cycling with application of salt by rain phase. One test cycle corresponds to one week of testing. The one-week test cycle is composed of two twelve-hour sub-cycles. Sub-cycle 1 consists of controlled and varied temperature and humidity, combined with salt application by salt spray exposure that consist of 0.5% NaCl solution. Sub-cycle 2 consists of constant temperature and humidity.

The variation in temperature is 25-50 degrees C and the relative humidity (humidity % RH) reaches from 70 to 95. The complete one-week test cycle consists of 5 repetitions of sub-cycle 1 followed by 2 repetitions of sub-cycle 2.

Corrosion resistance requirements

Corrosion resistance requirements for samples tested by Scania STD 4445 are specified by requirement standards. The requirements depend on the substrate and coating of the samples and the environment the samples are exposed to during position in the vehicle.

Example of requirement standards where accelerated corrosion testing by test method Scania STD4445 is required are: