New Approaches to Corrosion Protection

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Steel structures are protected against corrosion by zinc-containing primers. Zinc is mainly present in the form of zinc dust in high concentration. To ensure sufficient adhesion to the steel substrate even under difficult conditions, its surface must be carefully pre-treated and kept clean until application. This is difficult or very expensive to achieve in steel structures located in a heavily polluted environment or in a maritime atmosphere. A further disadvantage of the use of primary elements (primers) with a high zinc concentration is that the resulting zinc oxidation products are considered hazardous for water.

If highly effective zinc primers can also be formulated with reduced zinc content, the adhesion of the primer on the steel substrate, as well as the interlayer adhesion to the coatings, could be improved due to the higher proportion of organic matrix. Since the effectiveness of the zinc corrosion protection is essentially based on its electrical contact with the substrate, the zinc should remain conductive as long as possible for long-term corrosion protection, yet this conductivity must not facilitate the premature levelling of the zinc. As part of the publicly funded ZINCPOWER project, researchers therefore plan to examine the extent to which altering the pigment composition could eliminate the stated disadvantages and restrictions on the effectiveness of zinc primers. The following variants are to be tested and combined if necessary:

• Alteration of the particle size distribution and particle shape of zinc pigments
• Use of zinc alloy pigments
• Zinc pigment surface treatments
• Addition of zinc-free corrosion-inhibiting pigments

In particular, adding graphene appears to be promising for ensuring good corrosion protection with reduced zinc pigment concentration. Even with low pigmentation, this ensures improved adhesion and guarantees the conductivity and hence the effectiveness of the zinc-based corrosion protection even in later weathering phases. Furthermore, graphene additives can increase the wear resistance of coatings.