Corrosion handbook

14 06/21
2.2 Lab facilities/tests
At our in-house research facilities, Hilti performs the most relevant lab corrosion
tests available for our products (see Fig. 13).
Neutral salt spray test: EN ISO 9227, ASTM B117
The salt spray test is one of the oldest and most widely used accelerated
corrosion tests. The samples are exposed permanently to a saline fog made
from a five percent sodium chloride solution. The salt spray test is not directly
representative of corrosion protection in real atmospheres because of the high
chloride concentration and lack of dry periods. However, it is a practical test
primarily used for process qualification and quality acceptance. Hilti uses the
salt spray test to check the homogeneity of zinc coatings on fasteners as quality
control in production (see Fig. 15 and Fig. 14).
Zn alloy coatings like ZM and ZnNi coatings show a significantly better
performance in the neutral salt spray test.
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Fig. 15: Typical time until the first appearance of red rust (corrosion of the steel
substrate) in the salt spray for zinc and Zinc magnesium (ZM) coated products
with varying coating thickness.
Fig. 13: Picture from our corrosion
lab with various corrosion testing
chambers.
Fig. 14: Electrogalvanized screws with
around 5 µm zinc coating after 48 h (up)
and 96 h (down) in the salt spray test.