Ask The Expert: Zinc Platings or Zinc Flake Coatings?

Many of our customers are receiving requests to supply fasteners with a Zinc Flake coating.

Zinc Flake coatings are becoming the coating of choice for fasteners used in the automotive, construction equipment, heavy truck and agriculture markets. Manufacturers like Caterpillar, John Deere, AGCO, CNH and Bobcat are requiring the fasteners used to build and maintain their equipment to be coated with zinc flake coatings and are moving away from the more traditional zinc platings that they have used in the past.

Zinc flake is a generic name for a coating that contains zinc and aluminum flakes that are bonded to the fastener with a proprietary matrix. For fasteners, this coating is applied using a special Dip Spin process that does not use harsh chemicals, prevents embrittlement, and is environmentally friendly (RoHS compliant).

Traditional zinc platings (Zinc Clear, Zinc Yellow, etc) are applied using the electro-plating process. Electro-plating is very effective in applying a thin uniform coating on threaded parts but can cause embrittlement in high strength fasteners and some of the chemicals used are becoming restricted in some industries.

Zinc flake coatings provide superior corrosion protection compared to the standard zinc platings that are used today.

Coatings corrosion protection is tested using a Salt Spray cabinet. Every 24 hours in a salt spray cabinet is meant to represent several years in the real world. Standard Zinc platings provide 48 to 96 hours of salt spray testing depending on the thickness and the top coat that is applied (trivalent chromate, yellow chromate, etc) while a zinc flake coating can provide salt spray protections ranging from 480 to 1,000 hours, depending on the version that is applied.

There are four main brand names of zinc flake coatings:

• Geomet
• Magni
• Delta Protekt
• Dorrltech   

Each of these brand names comes in several versions, depending on the corrosion protection and special features that are required. Individual plating houses must be licensed by these suppliers in order to be able to supply these coatings. The equipment needed to apply these coatings is special so a sizeable investment is required by the plating house in order to apply these coatings.

Zinc flake coatings do have some limitations as compared to zinc platings. Zinc flake coatings tend to be applied at a higher thickness than an electroplated coating and can cause thread fit issues. Zinc flake coatings can also fill in recesses such as hex sockets, Philips or Torx drives. Most zinc flake plating lines are designed for high volume applications so small lot quantities can have high minimum lot charge.

If you have questions on a plating callout, just contact your Earnest representative and we can help you identify the type of coating you need.