HOW ZINGA WORKS...
Zinga was originally invented in Ghent University, Belgium, in the 1970's and has since been used in a wide variety of projects throughout the world. Click here for the typical applications of Zinga or here for a selection of testimonials.
BUT… Zinga is not a paint.
Zinga is an active zinc performance coating which works in conjunction with the metal beneath whereas paints are only passive barriers. Regardless of how thick paints are applied, they remain as barriers. Once they are breached corrosion sets in immediately. Despite this significant difference Zinga is still often mistaken for a paint simply because it’s liquid and comes in a tin. But there are other more subtle differences. For example it does not “skin over” in the tin because Zinga has an unlimited pot-life and it doesn’t go “tacky” like a paint.
Cathodic protection, or active protection, arises from the zinc (the anode) sacrificing itself in favour of the base metal (the cathode) with the resulting flow of electrons preventing corrosion’s chemical reaction. In this way the protection of the metal is guaranteed, even when the zinc layer is slightly damaged. Other well established methods of cathodic protection include hot-dip galvanising (HDG) and zinc thermal spraying both of which exhibit a constant sacrificial rate of the zinc layer.
Within Zinga though this sacrificial rate reduces dramatically after the zinc layer has oxidised and the natural porosity have been filled with zinc salts. Additionally the zinc particles within the Zinga layer are protected by the organic binder without adversely affecting the electrical conductivity. This enables Zinga to create nearly the same galvanic potential between the zinc and the steel as hot dip galvanising but with a lower rate of zinc loss because, put simply, the binder acts as a “corrosion inhibitor” to the zinc. Please see the Zinc Loss Prediction Chart further down this page for a estimate of expected zinc coating service life.
"The zinc in Zinga becomes the sacrificial anode in relation to the steel but it corrodes at a much slower rate than would otherwise be expected"
If the Zinga layer is sufficiently damaged to expose the base metal below, the steel would form a layer of surface rust but no corrosion would take place beneath it. In other words if the surface discolouration was removed the steel below would not be pitted or eroded. This is called "throw" and enables Zinga to protect bare metal up to 3 - 5mm or so away from where the coating ends – slightly less than new HDG. Zinc sacrificial anodes used on the steel hulls of boats below the waterline work on the same principle to protect metal in the surrounding area. Zinga is simply a different form of these anodes and is therefore sometimes referred to as a liquid anode or sheet anode when used in immersed conditions. However, it should be noted that like all forms of zinc protection, Zinga should not be used uncovered in immersed conditions above 65 degrees C as that is the inversion point where the steel starts to be sacrificed to protect the zinc. Click here to see relevant report from the BNF Fulmer Laboritory which evaluates this galvanic protection.
The ability of zinc to provide galvanic protection is a function of it’s weight per given area. Dry Zinga contains a minimum of 96% medicinal quality zinc by weight, the particles of which are significantly smaller and purer than those found in normal "zinc rich" coatings. The Zinga particles small size and elliptical profile ensures maximum contact between both the individual particles and the substrate. This greater density of active zinc per given area combined with the good conductivity of the layer ensures that charge flows through every millimetre that has been coated and therefore provides excellent cathodic protection.
Passive protection, such as paints and cladding, creates a "barrier"
between the steel substrate and the elements. Once this barrier is compromised
then the moisture and atmospheric salts will be able to start corroding
the steel beneath the damaged area. This corrosion will then begin to
creep extensively beneath the coating.
The corrosion rates of zinc in various environments have been well researched over the years. As a result it is possible to chart the predicted service life for a zinc layer at a given dry film thickness (DFT) in a particular situation. The chart below is based on Hot-Dip Galvanised steel but, as it has already been explained in the Active Protection section, Zinga performs at least as well as HDG in normal atmospheric conditions and even better in marine environments. Please note that the minimum acceptable DFT would normally be 50 microns i.e. the structure should be re-loaded with new Zinga once the zinc has depleted to 50um from its original DFT (normally >120um if using Zinga without topcoats). This is an important point as otherwise this chart could be misleading.
Source: SGS Axa-Med. Service Life is defined as the time to 5% rusting of the steel surface.
If Zinga is used as part of a duplex system, i.e. is over-coated with another compatible product, the top-coat provides the initial barrier but the zinc oxide will form a secondary barrier if the first layer is compromised for any reason. As the top-coat becomes naturally porous over time, the Zinga fills the pores from below with zinc oxides enabling the top coat to last longer. Additionally the Zinga does not even start to sacrifice itself until the topcoat is damaged exposing the bare zinc to the elements. It is because of this that Zingametall in Belgium state that the lifetime of a duplex system can be 50% more than the sum of the individual lives of Zinga and the topcoat.
Another of Zinga's unique characteristics is its ability to re-liquidise when a new coat of Zinga is applied to form a single homogenous layer. This ensures a massive cost saving in on-going maintenance because the old Zinga layer does not have to be removed before re-coating with Zinga. This also means that once the initial abrasive blasting has been completed the surface will never have to be blasted again.
The following microscopic photos demonstrate the total integration of multiple layers of Zinga:
For further information on the mechanism of Zinga's corrosion protection, please contact Zinga UK..