The use of single component water 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. Nevertheless, the challenge continues to find alternatives to the traditional chromate, zinc or similar heavy metal type corrosion inhibitors which tend to rely on passivation or sacrificial cathodic protection4. Additionally, ongoing regulatory developments, which require lower VOCs and elimination of carcinogenic materials continue to tighten the usage of products containing these heavy metals thus forcing the need for alternative technologies. The use of nano vapor phase corrosion inhibitors(VCIs) provide an attractive alternative by adsorbing onto the metal substrate and filling the voids or micro-crevices of the substrate and preventing corrosion from starting or growing once the surface of the coating has been damaged. This technology has been proven effective in single component water based coatings at dry film thickness(DFTs) of 1 mil(25 microns)2,5.

Four Learning Objectives

1. How VCIs work in a coating

VCIs are formulated into a coating thru a complex development process which involves determining chemical 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 adsorbing onto the metal surface in a non-reactive attractive capacity, in other words, they are attracted to the metal thru the particle charge1.

2. 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 can be illustrated as follows:

The larger platelets are representative of traditional inhibitors which are unable to fill the micro-crevices, leaving gaps where corrosion can start and/or grow3.

3. What type of coating systems can 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.

4. The 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 carcinogens for workers exposed to them. The environmental advantages of using VCIs are that they are non-toxic, do not contain heavy metals, and have no adverse effect due to their low usage concentrations. VCIs have long been used in other products such as PE films, foams, powders and liquids to provide a vapor phase of corrosion protecion without impacting the environment.

Key words: Conference papers, 2017 conference papers, water based coatings, corrosion inhibitor, vapor phase