On site Galvanic protection / upgrade
ZINGA PAINT MATERIALS
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 and once they are breached corrosion sets in immediately.
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. Zinga has a 3-5mm ‘throw’, which means that unprotected metal up to 5mm away from a Zinganized
surface will be protected. It will form a layer of surface rust, but there will be no pitting beneath the rust. On small areas like scratches
and chips, the surface will often go a light brown-grey colour but underneath no corrosion will take place.
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.
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.
With Zinga, the organic binder and the zinc oxide layer that forms on the surface create an impervious barrier by blocking the zinc’s natural
porosity with oxide particles. Unlike other passive coatings, once breached the zinc oxide layer simply renews itself by re-oxidising.
This layer of oxides is the reason behind the matt appearance of Zinga as opposed to the shiny hot-dipped finish.
Predicted Service Life
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.
If Zinga is used as part of a duplex system, i.e. is over-coated with another compatible product such as Tar Free Polyurethane MIO,
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.
The Tar Free MIO is a moisture-curing highly modified Polyurethane coating with the following attributes:
• It is a single-component coating. This means that there is never any wastage due to over-mixing and any material that isn’t used can
be re-sealed and used at a later date.
• The coating dries by evaporation but actually cures hard by exposure to the atmosphere.
• It can be applied directly over Zinga by either brush, roller or spray and eliminates the requirement for any primer.
Re-Liquidising of Zinga
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:
Fig.1A thin film of gold dust was applied on top of the first coating of Zinga
Fig.2 Seven days later a second coating of Zinga was applied on top of the gold dust.
It can be clearly seen that the gold dust has mixed completely within the two Zinga layers.
Fig.3 The same test was done with a zinc-rich paint. The gold film remains intact between the two coats demonstrating that
they remain as separate layers.
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 – see the link http://www.zinga-uk.co.uk/how.html.