Materials Performance Supplements


Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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High-Performance Water-Based Coating Enhanced with Nano-Vapor Corrosion Inhibitors Markus Bie B er, Cortec Corp., St. Paul, Minnesota, USA The use of single-component wa- ter-based coatings for protection of military metal substrates continues to grow due to their low odor, health and safety advantages, easy cleanup, and environmental friendliness. Neverthe- less, the challenge remains to find al- ternatives to the traditional chromate, zinc, or similar heavy metal-type cor- rosion inhibitors that tend to rely on passivation or sacrificial cathodic pro- tection. Additionally, ongoing regula- tory developments, which require lower volatile organic compounds and elimination of carcinogenic mate- rials, continue to tighten the use of products containing these heavy met- als, thus forcing the need for alterna- tive technologies. The use of nano-va- por phase corrosion inhibitors provides an attractive alternative by adsorbing onto the metal substrate and filling the voids or micro-crevices of the substrate and preventing corro- sion from starting or growing once the surface of the coating has been dam- aged. This technology has been proven effective in single-component water-based coatings at a dry film thickness of 1 mil (25 ┬Ám). In a 2002 study by NACE International, 1 the cost of corrosion for the U.S. Depart- ment of Defense (DoD) was estimated to be in excess of $20 billion. Traditional corrosion control methods for protecting metal sub- strates in the military include chromate, zinc, and other heavy metals in inhibitors working in conjunction with passivation or cathodic protection. 2 An environmentally friendly, effective alternative involves the use of nano-vapor phase corrosion inhibitors (VCIs) in coatings used to protect these assets. 3-4 VCIs and Coatings How VCIs Work in a Coating VCIs are formulated into a coating through a complex d e v e l o p m e n t p r o c e s s t h a t involves determining chemi- cal compatibility of the VCIs with the other components of the coating, such as the resin, solvents, pigments, and other additives used for a variety of reasons. VCIs work by adsorb- ing onto the metal surface in a nonreactive attractive capac- ity ; in other words, they are FIGURE 1 Use of traditional inhibitors with larger platelets can leave gaps in which corrosion can occur. attracted to the metal through the particle charge. 5 How VCIs Compare to Traditional Inhibitors VCIs compare with traditional inhibitor systems by using smaller particles as well as relying not only on contact inhibition but also vapor phase inhibition, providing more complete coverage and protection of the surface. This is illustrated in Figure 1. The larger platelets are representative of traditional inhibitors that are unable to fill the micro-crevices, leaving gaps where corrosion can start and/or grow. 6 Types of Coating Systems that Use VCIs VCIs can be used with most coating systems. There are many variations of VCIs and the key is to choose the correct VCI for the corresponding coating system by checking compatibility, effectiveness, and processability. Environmental Advantages of VCIs over Traditional Inhibitors Traditional inhibitors containing heavy metals are becoming increasingly more regulated and often are no longer allowed to be used due to the negative impact they have on the environment and as carcin- ogens for workers exposed to them. The environmental advantages of using VCIs are that they are nontoxic, do not contain heavy metals, and have no adverse effect due to their low usage concentrations. VCIs have long been used in other products PROTECTIVE COATINGS 20 JUNE 2017 MATERIALS PERFORMANCE CORTEC SUPPLEMENT TO MP

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