- Typical Applications
- Surface Preparation
- Curing Mechanism and Drying Times
As a repair for worn or damaged hot-dip galvanising or hot metal spray
This is probably the most common use of Zinga as it requires the simplest surface preparation (see Applying Zinga). Zinga’s mechanism of protection is so similar to conventional galvanising that they work in complete unison – after all they are merely different forms of zinc. Rather than replace galvanised assets, structures can simple have their protection “re-charged” by applying Zinga to the rough surface of the old galvanising after appropriate decontamination.
As a stand alone system without topcoats to replace hot-dip galvanising or hot metal spray
Zinga provides comparable protection to conventional galvanising without the need for topcoats. Although Zinga is only available in grey the significant advantage of this form of application is that the Zinga layer can be re-coated at any point in the future with the bare minimum of preparation without compromising the integrity of the coating (see Re-Liquidising of Zinga). Zinga on its own is often used when specifiers are unable to galvanise because the structure is already in situ or too big for the molten zinc baths. Additionally Zinga is commonly specified on delicate structures (wrought iron gates, sculptures etc.) or when architectural demands require a higher standard of surface finish (no need to drill to de-gas, fettle etc.).
As a primer with suitable topcoats
Not everybody likes the colour grey and with the additional protection of a compatible topcoat the coating durability offered is significantly increased. The Zinga does not even have to start actively working until the topcoat has been compromised and with no underlying corrosion creep or rust bubbling the topcoat itself inevitably lasts longer (see Duplex Systems for more detail).
As protection to concrete reinforcement bars (rebars)
Widely used in countries where the available aggregate for concrete can be saline (e.g. Iran , India, Saudi Arabia etc.), Zinganising the steel re-bars before assembly and immersion in concrete ensures vastly increased protection from corrosion without reducing the pull-out strength of the bars. Recent tests in three independent laboratories showed that Zinga had at least twice the corrosion protection of either galvanised or epoxy coated rebars. Please click here to read about this aspect of Zinga usage in greater detail (please note this is a comprehensive document and may take some time to download) or here for specific lab reports on the subject.
Firstly the surface will require to be decontaminated by steam cleaning or high pressure washing to completely remove salt, grease, old paint, loose particles etc.
With marine structures, all crustacean growth must be removed from the steel’s surface before the degreasing process begins, and not after.
If the Zinga is to be applied to old, worn galvanising, metallising or old Zinga then all that is required after decontamination is to ensure that there are no loose particles on the surface. Please contact ZingaMetall for a full specification.
If, however, the steel is either new or has not previously been galvanised then, after washing, the surface will require to be grit blasted to a cleanliness standard of Sa 2.5. The grit used should be carefully chosen to achieve the blast profile outlined in the appropriate specification (normally between 50 and 80 microns depending on application).
The chosen grit should always be able to achieve a blast roughness of 12.5 to 15 microns. It should be noted that UHP Blasting does not create a profile and should therefore not be used as the sole means of surface preparation.
Zinga can be applied in a wide variety of weather conditions . The application surface temperature range is from -15C to +60C where conditions allow with a maximum humidity of 95% so long as there is 3C minimum between the steel temperature and the dew point. Like all coatings the substrate surface should be free from all types of contamination. Please seek advice from the ZingaMetall Technical Department for extreme application environments.
The broad range of allowable application conditions that Zinga affords means that very few days are lost during projects due to poor weather i.e. the maintenance window is extended. This, combined with Zinga’s unlimited pot and shelf life, ensures minimal wastage of either time or materials during a project.
|Area = 1m||Blast Profile (Microns)|
|Dry Film Thickness (Microns)||40||60||80|
It is vital to note that before exposure to a saline environment (i.e. submerged in salt water or placed in a salt spray zone) any Zinganised surface will require saturation with fresh water for a minimum of two hours to properly seal it. If the coating is unlikely to be immediately exposed to salt then exposure to rain water over time will have the same sealing effect.
Approximate Drying Times (45µm dft) @ 20C:
- Touch dry in 10 minutes
- Dry to handle in 30 minutes
- Dry to overcoat with Zinga in 60 minutes
- Cured to overcoat with water-based paints in 4 hours
- Cured to overcoat with epoxy in 24 hours
N.B. Please see notes on the Zinga Application Data Sheet for greater detail.
Although Zinga can be easily over-coated with a wide range of topcoats, it should be noted 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. ZingaMetall regard the use of the “mist-coat/full-coat” technique as vital to prevent this happening. An MIO or equivalent epoxy sealer should first be applied in a very fine mist coat (no greater than 20-30µm) which when cured, seals the Zinga and provides a barrier to the solvent in the subsequent coat. The second full-coat of the tie-coat can be applied at the same d.f.t. as before but tight control is required to ensure the maximum combined d.f.t. of 90µm is never exceeded. Please observe the relevant manufacturers drying and curing times for the tie-coat before proceeding on to the top-coats. This is vital to ensure that all the solvent has evaporated and minimises the potential for solvent entrapment.
Some paint companies sell epoxies which are specifically designed for use as tie-coats. The resins that are used in these tie-coats are “thin” resins; hence they do not require the addition of solvent prior to spray application. Normal epoxies which do require solvent to be added before application must not be used as they increase the potential for solvent entrapment. Avoid this problem by always using a proper tie-coat.
Paint manufacturers normally specify individual primer/top-coat systems and these should always be adhered to and applied over the 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. It should also be noted that cellulose lacquers cannot be applied directly onto Zinga and an automotive MS primer must be used beforehand. High-build vinyls and chlorinated-rubber paints are extremely high in solvent content so the advice of the previous paragraphs is particularly relevant. ZingaMetall recommend, where possible, the use of water-based topcoats to complement the environmentally friendly properties of Zinga.
Alufer N (another Zingametall product – see Product Range) is widely used to seal the Zinga prior to the application of topcoats.
Zinga is a truly unique coating product so if you have any query relating to compatible topcoats please contact the ZingaMetall.