Results of Salt Spray Tests in Accordance with
DIN 50 021 Using CORRPASSIV
The (physically wetting) polyaniline primer CORRPASSIV was compared with a fast-drying two-component epoxy resin primer and a metal-reactive two-component primer with adhesion-promoting properties. All three primers were coated with a two-component polyurethane paint. CORRPASSIV, both with and without top coat, exhibited no rust formation beneath the primer. The slight undermining receded after the test, and even within the cross and scratch injuries it was virtually impossible to detect any corrosion.
The salt spray test was performed in accordance with DIN 50021 with an exposure time of 288 hours.
The primer was tested on one plate without top coat (with a cruciform injury site), and on another with top coat (with scratch damage).
Both coating systems were also assessed after the test for adhesion, using the cross-hatch test.
CORRPASSIV without top coat: no rust under cross-hatch cut
The cross-hatch test made it clear that the polyaniline primer displayed the best adhesion, and also that here the corrosion was confined solely to the damaged cross-hatch area and the undermining effect was by far the smallest.
The epoxy resin primers used for corrosion protection proved distinctly brittle and exhibited considerable rust formation beneath the layers peeling off.
Standard system: corrosion attack even under two-component primer
On the comparison specimens with clearly poorer adhesion properties, corrosion products were even found beneath the intact areas of primer, and the coatings displayed either considerable blistering or marked undermining in the region of the cross.
Metal-reactive two-component primer with top coat: cracking and considerable
undermining by rust
These results were confirmed in the specimens with polyurethane top coats.
Here too CORRPASSIV displayed outstanding results thanks to its excellent adhesion to substrate and top coat.
With all three coatings corrosion was visible at the scratch. Here CORRPASSIV displayed considerably less "bleeding" of corrosion products than the comparison specimens.
The combination of polyaniline primer / polyurethane top coat showed only a very small measure of undermining (0 - 0.5 mm).
CORRPASSIV with top coat: hardly any undermining, no flaking of paint system at
cross-hatch cut.
The comparison specimens exhibited varying degrees of marked undermining of the coating (up to 4 mm), sometimes with blistering as well.