Zinga Application

O'Grady Coating
Manufacturers (Pty) Ltd

Tel: 013 - 2462570
Fax: 013 - 2462573

> Zinga Application methods  |  > Zinga Lifetime and maintenance

Surface preparation

1. General rules for ZINGA
Working procedure
It is very important to keep the following order in mind:
a. eliminating dirt, grease, oil and salts
b. eliminating paint, rust and mill scale
c. roughening
d. dedusting or rinsing

Inorder to obtain a cathodic protection, an electric contact is required between ZINGA and its substrate. The substrate must therefore be cleaned to cleanliness degree SA 2.5. This means that it must be exempt of any impurity such as: dirt, grease, oil, salts, paints, rust and mill scale. However, ZINGA can be washed again with water to make sure that all remaining dust is cleared from the surface. A very good alternative for this cleaning procedure, is slurry-blasting.

Next to these, there are many other methods to obtain a clean surface, depending on the circumstances on the field or in the workshop. The method will also depend on the fact if the surface has been formerly zinganised or galvanised.

For detailed information, we refer to our technical specifications, available on request.

Time interval between surface preparation and application

The application should happen as soon as possible after the surface preparation in order to prevent the creation of new contamination on the surface, such as salts. However, the norms are not so strict for ZINGA as for a paint system: a little rust (flash rust) is not a problem for the application of ZINGA, nor is humidity. But, any other type of surface contamination must be eliminated.

2. General guidelines for different types of substrates

New or old steel without galvanising coating
First the surface should be cleaned by UHP water-jetting to remove dirt, grease, oil, salts, paint and rust. This must be followed by sand or grit-blasting to cleanliness degree SA 2.5 and roughness degree Ra 12.5µm to 15 µm, in order to remove mill scale and in order to obtain the necessary roughness. Afterwards the surface must be cleaned from dust by low-pressure water-cleaning.

For detailed information, we refer to our technical specifications, available on request.

New hot-dip galvanisation or new zinc-spraying
First of all UHP water-jetting is necessary to remove dirt, grease, oil, salts, paint and rust.
If the structure to be treated is only slightly oxidised or just weathered, rusty areas must locally be touched-up with one or more layers of ZINGA. The formation fo rust has created an adequate roughness profile to obtain a good adhesion between the ZINGA and the steel.
Afterwards the total surface can be completely coated with ZINGA , in order to recharge the existing galvanising layer. The surface must first be roughened with an etching product.

If the structure to be treated shows over 5% of rust, then this means that the cathodic protection of the steel is for over 50% used and local touch-up will not be sufficient. A surface preparation using blasting techniques is preferable. Afterwards the total surface must be completely coated with ZINGA.

For detailed information, we refer to our technical specifications, available on request.

New or old zinganisation
As explained above, each new layer of ZINGA makes the former layer liquid again, even years after the first application. Additional layers all blent to one single, homogeneous ZINGA layer. There is no risk for accumulation of layers that are different in structure, which could cause peeling off. The surface preparation before recharging is reduced to a minimum: you only need to clean the surface with water (low or high pressure, depending on the surface contamination).

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  Application methods

1. General rules for ZINGA

Layer thickness
The layer thickness of the first coat of ZINGA must not be too high: 40µm is perfect. If the layer is too thick, then the solvents cannot evaporate sufficiently, which causes solvent retention and there is also the risk of formation of pinholes.

The following layers, when applied by an airless spraying technique, can have a thickness of 60 to 80µm. The total layer thickness that is prescribed will depend on the used coating system (ZINGA is a unique system, ZINGA in a duplex system with topcoats, ZINGA on top of hot-dip galvanisation,...).

Theoretical spreading rate:
with 1Kg of ZINGA you can cover 3.54m² at a layer thickness of 40µm.

Drying time
ZINGA is touch-dry and dust-free in about 10 minutes, depending on the atmospheric conditions and the drying process. It is mechanically cured after approximately 48 hours.

ZINGA is a coating that is best applied in two layers. A new coating of ZINGA can be applied after one hour. In a duplex system, topcoats can be applied after 4 to 24 hours, depending on the drying process.

Environmental conditions

For the application of ZINGA there are only very few restrictions.

A few things that do need your attention:
In any environment invisible air contamination could be present. When the ZINGA is applied in a workshop, you must make sure that there is no diesel or silicone vapour in the air. When ZINGA is applied in a maritime environment, there can be a lot of salt in the air that contaminates the surface during application.
ZINGA can be applied in an atmosphere with high relative humidity. However, you must make sure that the ZINGA is applied at a temperature that is at least 3°C above the dew point.
Temperature and air circulation can strongly influence the drying and the polymerisation of the ZINGA coating.

2. General guidelines for different types of applications

ZINGA as a unique system
To apply ZINGA as a unique system is the ideal anti-corrosion protection. ZINGA is in a way a duplex system in itself because of its binder and the formation of zinc salts on the surface. The total layer thickness will depend on the environmental circumstances and the kind of structure.

In time the ZINGA layer will become thinner, because it sacrifices itself for the protection of the underlying steel cathode. After a certain time (depending on the original layer thickness and the environmental influences) maintenance will become a necessity. Due to the fact that ZINGA turns liquid again when a new layer of ZINGA is applied, tis system is also very economic whin it comes to maintenance. You only need to clian the surface with water and a new layer of ZINGA can be applied.
In order to fortify the ZINGA layer, the following procedure can be used: once the last ZINGA layer is touch dry, fresh water should be sprayed onto the coated surface until the ZINGA is completely saturated and does not absorb anymore water. This special treatment reinforces the formation of zinc salts and zinc carbonates, which makes the ZINGA layer better resistant ot atmospheric influences. It also accelerates the polymerisation process and it is very beneficial tor the adhesion of ZINGA.
150µm is the absolute maximum total layer thickness that we would prescribe for ZINGA as a unique system. Applying more than 150µm would not improve the efficiency of the cathodic protection any more.

For detailed information, we refer to our technical specifications, available on request.

ZINGA on top of hot-dip galvanisation and zinc-spraying
The galvanising film ZINGA recharges the old active layer and will offer a genuine cathodic protection. The ZINGA coation will start acting as the anode, sacrificing itself as time goes on and thus saving the hot-dip galvanisation. Only after full use of the ZINGA coating, the hot-dip galvanisation will take over the cathodic protection and will start functioning as anode.
The number of coats to be applied depends upon the remaining thickness of the hot-dip galvanising or zinc-spraying (metallisation) layer.

For detailed information, we refer to our technical specifications, available on request.

ZINGA in a duplex system
In some cases a duplex system is absolutely necessary, for instance if the metal structure finds itsesf in a chemically contaminated environment with a very low or a very high pH range. Or sometimes the structure requires a certain colour for visual recognition.

The application of the sealer or topcoat should be done with consideration for the drying period and before and surface contamination can occur. Follow the instructions on the data sheet of the product itself.

Zingametall offers different topcoats that are directly compatible on ZINGA. We also provide a number of compatible sealers. For any other product you must do a small compatibility test beforehand. In case topcoats from another supplier will be applied on top of ZINGA, Zingamettal should receive a written confirmation of the producer of the paint that it is compatible on ZINGA.

The recommended layer thickness for ZINGA in a duplex system is 60µm.

For detailed information, we refer to our technical specifications, available on request.

Information needed for correct advice
The correct advice for the surface preparation and the application of ZINGA, depends on a number of factors. Hereafter you will find some of the questions that should be answered, so that the ZINGA specialist can advise you exactly what system to use.

- What kind of steel is the structure made of?
- What is the condition of the surface before the application? (New or old steel? With or without coating?...)
- What kind of surface preparation is possible?
- In what kind of environment is the structure located? (Industrial, coastal or rural environment? Inside or
  outside? Immersed or underground?...)
- To what temperature range is the structure exposed?
- To what level of pH is the structure exposed?
- What should be the expected lifetime of the system?
- Are there any demands regarding the visual aspect? (Colour and gloss?)

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  Lifetime and maintenance

1. Life expectancy
ZINGA as a unique system

This diagram is based on the BBA certificate nr. 94/3042, issued by the British Board of Agrément, UK, that ZINGA has obtained. Concerning the durability of ZINGA is stated that ZINGA with a layer thickness of 60µm will remain effective:
- in excess of 20 years in interior conditions
- 20 years in rural conditions
- 12 years in inland industrial conditions
- 10 years in polluted coastal conditions

However, in view of our own experiences, we can confirm that figures on this diagram indicate an absolute minimum lifetime of ZINGA. In practice, ZINGA has a much better performance.

We refer to the application of ZINGA as a unique system on the Kalvoya Bridge in Norway in 1985. In 2000, 15 years after the application, the bridge was inspected and the layer thickness was measured. This report is very important because it gives us an idea of the estimated lifetime of ZINGA. (view)

Also take a look at the test report from the South African Bureau of Standards, dated 04/04/96. A salt spray test (400 hours) was performed on ZINGA in comparison to hot-dip, after which the loss in weight of the galvanising coatings was measured. (view)

As you can see, the table stops at 150µm. That is because 150µm is the absolute maximum total layer thickness that we would prescribe for ZINGA as a unique system. Applying more than 150µm would not improve the efficiency of the cathodic protection any more.

ZINGA in a duplex system
Lifetime duplex system = (1.8 to 2.5 ) x (lifetime ZINGA + lifetime paint)

The recommended layer thickness of ZINGA in a duplex system is 60µm. In an industrial environment, the lifetime of the ZINGA will be at least 12 years. If the expected lifetime of the topcoat is for instance 4 years, then the total expected lifetime of the duplex system will be 29 to 40 years.

2. Maintenance on ZINGA as a unique system

Periodic inspection, touch-ups and recharging
Maintenance should be conducted before the steel substrate has become exposed. Periodic inspection to determine the thickness of the ZINGA coating is of prime importance, especially in a very aggressive industrial or martime environment.

In case there has been mechanical damage, the ZINGA coating can be repaired with local touch-ups. Welding is possible on top of ZINGA. After the welding, the welding seam has to be cleaned and roughened. Then a new application of ZINGA can be done locally, on top of the welding. Keep in mind that zinc is too soft to be included in high performance welding.

In case 5 to 10 % of the total surface is corroded, a new ZINGA application on the total surface will be necessary. The ZINGA coating can be maintained on site. We call this recharging. This way the ZINGA can infinitely protect the steel substrate.
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