A popular standard for testing corrosion properties of vehicle paints

Introduction

The VDA 621-415 cyclic laboratory test, developed more than 25 years ago has served as the standard corrosion test for automotive coatings and substrates.

The test standard was developed by paint manufacturers in conjunction with automotive paint users to evaluate the corrosion resistance properties of vehicle paints through accelerated laboratory testing.

Although this test standard has largely been superseded by VDA 233-102, it still remains popular with many manufacturers in the automotive industry.

Conditions

Test specimens are placed inside and enclosed chamber and exposed to cycles of;

Continuous indirect spray of salt water solution (also referred to as fog or mist) which falls-out on to the specimens at a rate of 1.0 to 2.0 ml/80cm²/hour, in a chamber temperature of +35C. The pH of the salt solution fall-out should be maintained at a neutral pH ((pH 6.5 to 7.2 – this is also commonly referred to as NSS, which stands for Neutral Salt Spray).
Controlled temperature of between 18 and 28C and controlled humidity to represent ambient conditions.

Method

The testing is performed by placing prepared test samples into a chamber designed in accordance with DIN 50 017 and DIN 50 021.  The panels should be scratched all the way down parallel to the longitudinal side, multiple scratches can be made on the same test subject but should be at least 3cm from the edge and 5cm apart.

The test cycle should last 7 days and should consist of;

• 24 hours of SS DIN 50 021 salt spray testing.
• 96 hours (4 x 24 hour cycles) of KWF DIN 50 017 saturated atmosphere testing.
• 48 hours (2 x 24 hour cycles) at room temperature -18 to 28C as DIN 50 014.

The total test period is variable and will need to be agreed, but ideally should be 4 to 6 cycles corresponding to 4 to 6 weeks.

Once completed the panels should be rinsed off in clear flowing water and blown dry, if necessary by compressed air.  They can then be examined for visible changes, the extent of under-rusting on both sides of the panel evaluated.

Typical Application

Developed specifically for the automotive industry the test is specifically configured to demonstrate the effect of the formation of rust arising from damage to the vehicles surface paint, as well as rim / edge rusting.

If you would like further information please call our experienced team on 01827 318040 or email sales@ascott-analytical.com