What is the primary test for evaluating the corrosion resistance of this coating?

The Neutral Salt Spray (NSS) test, conducted as per IS 9844. The required duration of resistance without red rust is specified in Table 1.

What is a typical thickness for a zinc flake coating?

The thickness typically ranges from 8 to 20 micrometres (µm), depending on the performance class required. (See Table 2).

How is the coefficient of friction controlled for coated fasteners?

It is controlled by applying an integral lubricant or a separate top coat. The required friction range is specified by the purchaser based on Table 1.

Does this coating process cause hydrogen embrittlement?

No, because it is a non-electrolytic process. This makes it a preferred choice for high-tensile fasteners and components.

IS 15488

: 2004

Zinc Flake Coatings for Protection of Ferrous Components Against Corrosion - Specification

CurrentSpecializedSpecificationMaterials Science · Painting, Coatings and Surface Finishing

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This standard specifies the requirements for non-electrolytically applied zinc flake coatings designed for the corrosion protection of ferrous components. It classifies coatings based on their performance in salt spray tests and their coefficient of friction, covering aspects like thickness, adhesion, and material composition.

Specifies requirements for zinc flake coatings applied to ferrous components for corrosion protection.

Quick Reference Values

Typical Coating Thickness8 to 20 µm

Typical Curing Temperature Range200 to 300 °C

Minimum Salt Spray Resistance (Class A1)240 hours

Minimum Salt Spray Resistance (Class A4)1000 hours

Coefficient of Friction Range (for fasteners)0.08 to 0.18

Hexavalent Chromium (Cr VI) Content Limit (for Cr VI free)0.1% by weight

Practical Notes

A major advantage over galvanizing is the absence of hydrogen embrittlement risk, making it suitable for high-strength steels (strength > 1000 MPa).

The specification covers both systems with and without hexavalent chromium (Cr VI). Cr VI-free coatings are required for compliance with environmental regulations like RoHS and ELV.

A separate top coat is often applied over the zinc flake base coat to enhance corrosion resistance, provide color, and control the coefficient of friction.