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Efficient Specification for Preventing Oxidation of Galvanized Steel

What is Galvanized Steel

The technique of “putting a protective zinc coating on iron or steel to prevent rusting” is known as galvanization. Thermal diffusion galvanizing (also known as “Sherardizing” after the process’s creator, Sherard Osborn Cowper-Coles), hot dip galvanizing, electro plating, mechanical plating, painting with zinc-rich coatings, and zinc-spraying (also known as “metallizing”) are all methods for galvanizing steel.
We look at how galvanization helps improve the strength, durability, and appearance of steel. We also debunk the myths that galvanized steel can’t be powder coated and has a limited warranty and design life.
The most prevalent technique is hot dip galvanizing. The steal is dipped into a bath of molten zinc at high temperatures (about 450°C) throughout this procedure. Zinc oxide is formed when zinc interacts with oxygen in the environment, while zinc carbonate is formed when zinc combines with carbon dioxide. Zinc oxide and zinc carbonate combine to give galvanized steel its distinctive drab grey look while also preventing corrosion.
Galvanization is suitable for extruded and sheet metal products.
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The Shortcomings of Galvanization

While galvanization is a good way to prevent corrosion, it has a few drawbacks. While hot dip galvanized steel is intrinsically resilient, it might experience accelerated zinc substrate corrosion in greater corrosivity zones, reducing its total service life. The following are the applicable Australian Standards for steel and zinc corrosion rates under various air conditions:
• AS 4312 Atmospheric corrosivity zones in Australia;
• AS/NZS 2312.2 Guide to the protection of structural steel against atmospheric corrosion by the use of protective coatings – Hot dip galvanizing.
The application of an appropriate coating to insulate the zinc from the atmosphere and environmental factors can contribute to a longer shelf life if the coating offers adequate coverage and integrity. Powder coatings are a sort of coating system that can improve the durability, performance, and corrosion resistance of galvanized steel. By establishing a barrier layer with relatively high ohmic resistance between the substrate and the corrosive environment, such a coating can safeguard steel substrates.
Hot dip galvanizing and zinc spraying and coating, on the other hand, are intrinsically unstable. This is because they create a sacrificial layer on top of the steel that might cause powder coating finishes to fail. Because powder coatings are porous, oxygen can penetrate the zinc layer and cause oxidation or rusting. The powder coat will chalk, peel, or crack as a result of the oxidation process, lowering its look and performance.

Powder Coatings: Key Considerations

Recent improvements in coating technology have relieved some of the frequent difficulties related with the application of powder coatings on galvanized steel. Leading powder coat manufacturers provide innovative coating methods that compensate for galvanizing’s drawbacks. In compared to single-coat powder coating procedures, using a two-coat system – in which a barrier primer is used to insulate the top powder coat layer from the zinc layer, therefore protecting the zinc layer from the environment – can give superior uniformity, coverage, and protection.
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Power coatings also provide a number of aesthetic advantages.

Powder coatings, when applied by a professional operator, may provide more detailed forms and finishes than traditional paints. Conventional paints and other organic materials may also degrade due to solar radiation, and if the paint system is too thin, regions of increasing zinc thickness may be apparent beneath the finish.
It is important to note that careful surface preparation, uniform coverage, and skilled thorough application of any coating system are required to achieve aesthetic and performance requirements.
Designers and specifiers should prefer: coating system providers with appropriate experience and track record, products with proven lifespan, long term warranties, and evidence of performance and compliance with the Australian building code.

Compliance

Products required for warranties meet the requirements set by the Standards Australia, Under the Building Code of Australia (BCA), specifically:
• AS 4506 Metal finishing – Thermoset powder coatings;
• AS 3715 Metal finishing – Thermoset powder coating for architectural applications of aluminium and aluminium alloys;

Sustainability

Powder Coatings which are Green Building Council of Australia approved, do not contain organic solvents and release zero volatile organic compounds.
Get Green Star points for sustainable construction projects by opting for powder coating which are Green Building Council of Australia approved.
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