VDA 621-415 Testing the Corrosion Protection of Vehicle Paint with Alternating Cycle Test

A corrosion chamber is used when applying the test method described in the standard “VDA 621-415 Testing the corrosion protection of vehicle paint by alternating cycle testing” published by the German Automotive Industry Association (VDA).

This testing method involves a 7-day cycle consisting of the following steps:

• Salt spray at 35 degrees plus/minus 2 degrees for 24 hours
• 40 hours condensation at 2 degrees plus/minus 8 degrees humidity, 100 percent relative humidity
• 23 degrees plus/minus 2 degrees with 16 hour control humidity, 50 percent (maximum 100 percent relative humidity)
• 40 hours condensing humidity at 2 degrees plus/minus 8 degrees, 100 percent relative humidity
• 23 hours controlled humidity at 2 degrees plus/minus 16 degrees, 50 percent (maximum 100 percent relative humidity)
• 40 hours condensing humidity at 2 degrees plus/minus 8 degrees, 100 percent relative humidity
• 23 hours controlled humidity at 2 degrees plus/minus 16 degrees, 50 percent (maximum 100 percent relative humidity)
• 40 hours condensing humidity at 2 degrees plus/minus 8 degrees, 100 percent relative humidity
• 23 hours controlled humidity at 2 degrees plus/minus 16 degrees, 50 percent (maximum 100 percent relative humidity)
• 23 degrees plus/minus 5 degrees for 48 hours with controlled unspecified relative humidity (e.g. 50 percent (maximum 100 percent relative humidity)

The corrosion chamber is loaded with test samples according to customer's request or in accordance with the VDA 621-415 standard (60-75 degrees from the horizontal).

All measuring equipment must be calibrated. The recalibration date must not be within the test period. The corrosion chamber must be calibrated for at least room air temperature and relative humidity. If necessary, the following room elements can also be calibrated:

• Room air saturation temperature
• Room air pressure gauge (atomizer pressure)

Peripheral devices should also be calibrated before use and may include:

• Handheld pH meter: Calibrate using buffer solutions and following manufacturer's instructions. The first solution should have a pH of 4.01 and the second solution should have a pH of 7.01. Acceptable tolerance is plus/minus 0.01. After completion, the electrode is rinsed using the electrode rinse solution. The buffer solution must be certified according to the National Institute of Standards and Technology reference material.
• Salinity refractometer: The refractometer is calibrated using the calibration solution (3,5 percent) of the calibration fluid.
• Conductivity meter: It is calibrated using the standard solution used to check the conductivity of water used in salt solution.

When necessary, room temperature and relative humidity are continuously monitored using an independently calibrated data logger.

During the salt solution exposure process, collection rates are monitored manually using collection cups placed at sample height. Collection rates should be in the range of 1-2 ml/h/80 cm2.

The VDA 621-415 standard refers to the “DIN 50021 Salt spray test” standard for the salt spray phase. Exposure to the salt solution occurs by atomization using compressed air. The DIN 50021 standard requires that the air delivered to the spray nozzles is heated and humidified by passing it through an air saturator. For the air saturator temperature value, which is directly dependent on the air pressure at the nozzle, see the table in the test standard (corresponding pressure gauge on the front of the chamber).

Briefly, this test procedure was developed to evaluate the corrosion protection of vehicle paintwork using an accelerated laboratory test. It is claimed that tests performed according to this procedure can produce results that correlate well with those seen in vehicles driven. This test is cyclical in nature, meaning that test specimens are exposed to changing climates over time.

Test specimens are placed in a closed chamber and exposed to a changing climate consisting of repeated cycles. The number of cycles and hence the duration of the test are variable.

The test exposure conditions apply as follows:

• Samples are placed in the chamber according to the test standard (60-70 degrees) or customer requirements.
• It is necessary to ensure that no sample shadows other samples and that droplets from one sample do not fall on other samples.
• Photographs are taken before the test begins and at the times specified by the customer.
• The test cycle is started and the test parameters are initially recorded

Among the numerous tests, measurements, analyses and evaluation studies carried out for businesses in various sectors, our organization also provides testing services defined in the standard “Testing the corrosion protection of vehicle paint with VDA 621-415 Alternating cycle test” with its trained and expert staff and advanced technological equipment.