Mild steel panels were used for the laboratory salt droplet test and
prepared by abrasive blast cleaning. All sharp edges and corners were
rounded, with the faces sufficiently polished to obtain a smooth and
even surface. All procedures during preparation and coating of test
panels closely resemble normal production practice. The panels were
sprayed with two different C-Ramic formulations to coat approximately
77% of each surface under test. The bottom section of each test panel
(approximately 23%) was left uncoated to allow corrosion to take place
in that area.
This was done instead of inflicting preliminary damage to the coating
by the specified scribing method as described in ASTM D 1654 (it is
not possible to obtain a definite cut line through the finished C-Ramic
coating by scoring with a scribing tool). After completing the coating,
the back of each test panel including edges was protected with a suitable
paint.
The thickness of C-Ramic coating was then measured using a Mikrotest
thickness gauge. Six coating thickness readings were taken on each test
panel and an average value calculated and recorded. The test panels
were then exposed to droplets using the salt solution described by the
Australian Standard 1580 Method 432.2 "Resistance to Corrosion - Salt
Droplet Test'.
Test panels were inspected visually at 500, 750, 1000, 1500 and 2000
hours and photographs taken. The continuous immersion for 2000 hours
in the solution (3 times the concentration found in normal salt water)
could not break the protective barrier offered by C-Ramic's corrosion
resistant coatings. The test was terminated after 2000 hours exposure,
as it was deemed unnecessary to proceed any further.
This salt droplet test has clearly proved that C-Ramic coatings provide
absolutely outstanding performance in a corrosive environment.
The lines at the interface of the coated and rusty sections (23% uncoated
area) on the test panels exhibited negligible underline coating deterioration
due to creeping corrosion. The thermochemically bonded nature of the
C-Ramic coating combined with a non-wetting action, provides the basis
for this excellent performance.
