Heubach’s Anti-Corrosive Pigments
“Nothing is as sustainable as anti-corrosive pigments.”
Who is not familiar with the discussions on the state of infrastructure in industrialized countries? Every day there are reports of another restriction on a highway bridge, or of another railroad line that has to be upgraded. The fact that these installations, some of which are more than a hundred years old, have withstood the test of time is due in no small measure to the coatings used for protection, which contain anti-corrosive pigments to ensure proper functionality.
Learn more about Heubach’s range of anti-corrosive pigments
Zinc orthophosphate ZP 10 & ZP 10 BS
Heubach GmbH started producing zinc phosphate 40 years ago. At that time still dismissed as a “green alternative” to the Cr6+-containing materials used as standard, such as zinc chromate, strontium chromate or zinc tetroxy chromate, zinc phosphate has gradually established itself as a universally applicable anti-corrosive pigment, and is still a popular and recognized product for a wide range of anti-corrosive applications.
Modified zinc orthophosphates HEUCOPHOS® ZPA, ZPO, ZMP
Unlike materials that contain Cr6+, zinc orthophosphate only acts in anodic areas via a passivation mechanism of the surface (cannot intercept electrons in the cathodic area to prevent the development of hydroxide ions involved in the formation of rust). According to current theory, zinc orthophosphate releases small amounts of phosphate ions in the coating and adheres as a metal phosphate complex to the surface to be preserved, thus protecting it.
Zinc orthophosphate can be used for a wide range of applications. The need for increased electrochemical effectiveness, in particular, was met by appropriate modifications: By introducing alternative cations such as aluminum and other modifiers, for example, solubilities are changed, electrochemical properties are added, or pH-value effects are achieved to suppress the formation of hydroxide ions in the corrosion process. These pigments are more effective than zinc orthophosphates and are used routinely in industrial or refinish coatings. However, the modification also causes the universal applicability to be restricted, which means that binder-specific products must be used.
Wide-spectrum anti-corrosives HEUCOPHOS® ZCP PLUS & ZAM PLUS
Manufacturers of coatings would prefer to continue using a universal pigment for logistical reasons. This demand can be met with the products HEUCOPHOS® ZCP PLUS and HEUCOPHOS® ZAM PLUS. While HEUCOPHOS® ZAM PLUS represents a sophisticated combination of the mechanisms of action of HEUCOPHOS® ZPA/ZPO/ZMP, HEUCOPHOS® ZCP PLUS was developed as a new, independent product. It additionally contains the positive properties of silicate chemicals, and also creates a physical barrier, which makes it the ideal pigment for the “one-for-all” approach.
Polyphosphates HEUCOPHOS® CAPP, ZAPP, SAPP, SRPP
Despite the increased effect of the modified orthophosphates, the desired effect was still not achieved in some applications compared to materials containing Cr6+. Modified polyphosphates were therefore developed as a further alternative. The different approaches involving calcium, strontium, zinc or silicon allow for possible changes in the solubility or availability of the inhibiting components. The polyphosphates have been shown to be very effective in special applications, but are also binder-specific. In addition to the anti-corrosive properties, there are also advantages in other paint properties; for example, HEUCOPHOS® SAPP used in 2K-PUR systems increases the pot life.
The anti-corrosive properties of silicon have already been described for the modified ortho- and polyphosphates. There is also a silica-based product, our HEUCOSIl™ CTF (Coil Thin Film). Originally developed for coil coating applications with polyester binders, the product can also be used in other industrial coatings. The mechanism of action of this calcium-ion exchange pigment is assumed to be the passivation of the metal surface due to metal silicate formation and a neutralization of the corrosion-stimulating ions by integration into the silica.
Non-zinc anti-corrosive pigments
There are also products that do not contain zinc for all applications. Nowadays they are the basis for the formulation of paints/coatings that do not require special labeling. This creates new possibilities, especially in the DIY sector, but also in the field of logistics (storage of coatings, disposal of residual containers, etc.).
The most recent zinc-free product development was HEUCOPHOS® CMP, a modified orthophosphate with the same effectiveness as the modified zinc-containing products, but with a reassuringly high level of universal applicability.