Zinga As Part Of A Duplex System
If Zinga is used as part of a duplex system i.e. it is over-coated with a compatible paint system, the top-coat provides the initial barrier to the elements, but the zinc oxide will still form a secondary barrier if the outermost layer is compromised in any way. As the paint top-coat naturally begins to break down and become porous over time, the Zinga fills the pores from below with zinc oxides enabling the top coat to last longer. Additionally, Zinga does not even start to sacrifice itself until the topcoat has become damaged to the point where it is exposing the bare zinc to the elements. It is because of this that we can state that the service-life of a duplex system can be 50% more than the sum of the individual lives of Zinga and the paint topcoat when added together.
Always strictly adhere to the appropriate specifications provided by the topcoat manufacturers in conjunction with Zinga. Although Zinga can be easily over-coated with a wide range of topcoats, it should be noted that when using epoxies etc. that Zinga is sensitive to solvents and all the necessary precautions should be taken to minimise its exposure to any solvents contained in the topcoats.
Zinga UK regards the use of the “mist-coat/full-coat” technique as vital and mandatory to prevent this happening. An MIO epoxy sealer such as Zingaceram EP MIO HS should first be applied as a very fine mist coat (no greater than 30-40µm) which when cured will seal the Zinga and provide a barrier to the solvent in any the subsequent coats. The second light coat of the sealer can be applied at the same DFT as before, care should be taken to ensure that the two combined layers do not exceed 90-100µm DFT. Please observe the relevant manufacturer’s drying and curing times for the tie-coat before proceeding to application of the top-coats. This is important to ensure that all the solvent has evaporated and minimises the potential for solvent entrapment.
Paint manufacturers will often specify a particular individual primer / top-coat systems, and these should always be applied over the correct tie-coat. Topcoats to avoid using in conjunction with Zinga include all alkyd-based enamels, which must never be applied over any zinc based coatings. This is because the zinc reacts with the alkyd and causes saponification which allows the paint to dry but to never harden and cure.
High-build vinyls as well as acrylated and chlorinated-rubber enamels are extremely high in solvent content, so the use of a sealer is mandatory with these coatings. Zinga UK recommend, where possible, the use of water-based topcoats to complement the environmentally friendly properties of Zinga. Alufer N is widely used to seal the Zinga prior to the application of topcoats.
It should be noted that cellulose lacquers cannot be applied directly onto Zinga, as the esters they contain will attack the binder. 2K automotive primers must be applied onto the Zinga layer beforehand, and then virtually any topcoats can be used.