Results of DECHEMA Tests on
CORRPASSIV
The polyaniline primer CORRPASSIV (with an epoxy resin top coat) on sandblasted St 37 steel was compared with specimens coated with only an epoxy top coat or with a zinc-rich primer and the same epoxy resin top coat.
The test investigated crevice and pitting corrosion in accordance with ASTM G-48 in FeCl3 solution and contact corrosion with copper (with short-circuit -- in accordance with DIN 50 919 -- and without short-circuit). For crevice and pitting corrosion testing was performed on specimens with intact coatings and specimens with deliberately damaged coatings.
The results were as follows:
Of the steel specimens with damaged coatings, only those treated with the polyaniline primer CORRPASSIV passed the test. With intact coatings the specimens with zinc-rich primer and with CORRPASSIV primer passed. Corrosion was nevertheless found to be considerably less marked with the PAni primer (Fig.1; Fig.2: crevice corrosion of specimen with zinc-rich epoxy primer).
The specimens without primer failed the test.
The contact corrosion tests were performed in each case with a defined cruciform injury to the coating and an insulating bolted joint to copper.
In the test without short-circuit only the steel specimen treated with polyaniline primer displayed no corrosion attack at the damage site and no undermining of the coating. The comparison specimens displayed more or less marked rust formation at the damage site.
In the test in accordance with DIN 50 919 with short-circuit by an external electrical connection to the contact corrosion element the cell current is measured directly.
All specimens exhibited formation of corrosion products in the crevice, but in the case of CORRPASSIV this was only slight (Fig.3 below).
The specimen coated with polyaniline primer recorded a current of only approx. 1 mA, whereas the comparison specimens with and without zinc-rich primer showed much higher readings (around 2.5 - 3 mA).
The official report is available in unabridged form complete with photos and diagrams.