Volvo STD 423-0069 Accelerated Corrosion Test, Version II (ACT II) - Cyclic Atmospheric Corrosion Test with Salt Load

The standard "Volvo STD 423-0069 Accelerated corrosion test, version II (ACT II) - Cyclic atmospheric corrosion test with salt load" developed by the Volvo car company describes the laboratory accelerated atmospheric corrosion test method. The purpose of this test method is to evaluate the corrosion resistance of metals in environments with significant chloride ions, primarily marine sodium chloride or winter road deicing salt.

This test serves as a general purpose atmospheric corrosion test and is applied to a variety of materials, coatings and material interactions in the form of test pieces or engineered components.

This method can be used as a design validation method to:

• Developing and qualifying new corrosion resistant products
• Developing new pretreatment and finishing processes
• Choosing the materials
• Perform quality control of finished products

This standard includes controlled conditions for equipment and procedures to allow testing to be performed with a high degree of repeatability and reproducibility. It is designed to be suitable for operation in a variety of climate chambers, either as a fully automatic procedure or with partially manual operations. The workday test procedure consists of:

• 6-hour wet phase at room temperature, intermittent exposure to saline solution (0,5 percent sodium chloride)
• 2,5 hour transition phase with drying under climate control
• 50 hour phase with constant temperature and humidity (70 degrees Celsius and 15,5 percent relative humidity)

After repeating this procedure Monday through Friday, a 50-hour weekend phase is added under constant climate control (70 degrees temperature and 48 percent relative humidity).

This standard method, herein referred to as ACT II, ​​differs in some aspects of corrosion from the previously published test described in the STD 423-0014 standard, herein referred to as ACT or ACT I. The differences are as follows:

• The test method is applicable to painted aluminum, unlike the STD 423-0014 standard.
• This method is more suitable for corrosion testing of magnesium, especially under bimetallic influence (due to longer macrowet time)
• This test is less effective for pitting aluminum and staining anodized aluminum due to the lower frequency of humid to semi-dry cycles.
• Austenitic stainless steels may exhibit exaggerated red rust due to relatively high exposure temperature combined with cyclic drying (above the critical pitting temperature)

The daily testing schedule consists of three basic exposure modes:

• A continuous wet phase at 0,5 degrees plus/minus 25 degrees in which test pieces are exposed to a 2 percent sodium chloride solution. The wet condition is maintained by intermittent spray exposure without drying and by temperature control or by setting the humidity control high enough to practically prevent drying.
• Two-stage transition from wet climate to controlled humid climate.
• A period under constant temperature/humidity control, 50 degrees plus/minus 0,6 degrees and 70 percent plus/minus 3 percent relative humidity. This is the condition to be maintained on weekends.

Exposure to 0,5 percent plus/minus 0,05 percent sodium chloride solution should occur at the beginning, middle, and end of at least the 6-hour wet phase. The wet phase should be incorporated into a fully automated test procedure or be subject to a partially manual process.

When performing a fully automated test procedure, the first spraying phase may consist of a longer spraying period (up to 50 minutes) to cool the test objects and the chamber more efficiently than the 70 degree temperature, 10 percent relative humidity condition. If all testing operations are carried out in the same climate chamber, it is important to follow the first spraying phase with efficient cooling to reach a temperature below 30 degrees within the first 30 minutes of the wet phase. After such cooling, some drying occurs, it is recommended to perform another short spraying phase to ensure that the solution in the samples has the prescribed concentration. The target temperature of 25 degrees plus/minus 2 degrees should be reached within the first hour.

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 “Volvo STD 423-0069 Accelerated corrosion test, version II (ACT II) - Cyclic atmospheric corrosion test with salt load” with its trained and expert staff and advanced technological equipment.