Zinc Coating Basics

Impreglon Australia offers three types of zinc coatings to our customers.

Zinc Electroplating

This is the long established and very common finish that is seen on many products generally intended for internal use. It can be either silver or the now less common yellow chromate seal.

The coating process involves cleaning to remove all surface contaminants, followed by the electroplating process where the part is immersed in a vat of specially formulated zinc chemistry. A DC current then deposits the zinc onto the work. The electroplating process will deposit thicker coatings on the outside edges and a lesser thickness in the recesses. In deep recesses, there may be no coating at all, which can become a source of corrosion.

Most zinc electroplated coatings have an added post plating conversion coating treatment, which will further enhance the corrosion resistance.

Zinc Flake

These coatings have been sold under a number of trade names for many years, but have recently become more readily available. The coatings have very good corrosion resistance and are now used for many industrial applications.

The coatings are liquid and they contain zinc and aluminium powders which take the form of very small flakes which overlap to form a highly efficient galvanic coating. Commonly treated parts range from small nuts and bolts processed in bulk to larger parts that are sprayed with conventional or electrostatic spray guns. Many of these coatings can be top coated with special sealers to further enhance the corrosion resistance. These top coats can be coloured if required and can also incorporate additives to decrease torsion in threaded applications.

Zinc flake coatings fit into service conditions between zinc electroplating and galvanizing.

As with most finishing applications, surface preparation is critical for a satisfactory performance. This can take the form of either abrasive or chemical conversion coatings.

Being a liquid coating, there can be some filling of small holes, screw heads etc. which may present a problem on some parts.

Zinc Phosphate

These are chemical coatings applied either by dipping or spraying and are generally applied to a clean steel surface. The coatings on their own have limited corrosion resistance and are generally post-treated with oils or other sealants. Most commonly, these coatings are used for subsequent painting or finishing with other organic coatings.

Combination coatings

All of these coatings make excellent undercoats for powder, e-coat or paint to give greatly increased corrosion resistance.

Why Choose Us?

  • Access to a world-wide zinc coating knowledge base.
  • In-house quality and testing team.
  • In-house corrosion testing facilities.
  • One to one million component capabilities.
  • A true ‘one-stop-shop’ for all your coating needs.

Zinc Plating

Zinc Electroplate

Zinc electroplating is a process in which a layer of zinc is bonded to steel in order to protect against corrosion.

Zinc Flake

Zinc Flake

A zinc flake coating is a non-electrolytically applied coating, seen here applied to steel. It provides very good protection against corrosion.

Zinc Phosphate coatings

Zinc Phosphate

A zinc phosphate coating as applied to an automotive clutch component.

More on Zinc Coatings

Thickness: 5 to 30 µm

Uniformity: Can vary greatly in thickness.

Hardness: Generally, it’s a soft metallic coating.

Wear resistance: These coatings have limited wear resistance.

Gloss: Coatings are for industrial use and tend to be semi-gloss metallic.

Colours: In standard form, the coatings are silver or yellow gold  in appearance but they can be top-coated with a tinted product.

Flexibility: Limited.

Toxicity: Not approved for food contact.

Corrosion resistance: Very good.

Chemical resistance: Most zinc coatings have limited resistance to acids, but can perform under acid conditions better than Hot Dip Galvanising. Topcoats improve their chemical resistance.

Hydrogen embrittlement: No hydrogen embrittlement on high strength steels.

Standards: There are automotive manufacturers standards (i.e. for fasteners) for these finishes from General Motors, Toyota and Ford to name just a few.

Conductivity: These coatings are electrically conductive although topcoats can effect this.

Cost: Generally, these engineering-type coatings are more expensive than many other more common coatings. Our charges will be subject to a number of factors such as volumes, processing conditions, and rack requirements. Like many of our processes, the labour for racking, un-racking, inspection and packing play a very significant part of our overall charges. Please contact us to find out more.

Size limitations: Subject to the application method, Impreglon can coat large components.

Recommended Uses

Zinc flake coatings play an important role in corrosion prevention of steel and iron products. It can be used as an undercoat for powdercoat or e-coat for added performance.

Before we process any work, we always provide a specification or a service requirement for zinc coatings so we can ensure our process meets all your needs, no matter how great or small.

Download our Zinc Coating Fact Sheet

Want more information, or prefer to download something to read later? No problem at all.
Here’s a downloadable .pdf document that covers off all of our service details so that you can read more or share it with a colleague.

IMPREGLON ZINC ELECTROPLATING FACT SHEET.PDF  |  IMPREGLON ZINC FLAKE FACT SHEET.PDF

Zinc Coating Case Study: Atotech Windmill Bolts

Atotech knows that when they need the best possible zinc flake coatings, Impreglon Australia are the experts.

READ MORE

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