The Paints, Varnishes and Related Products Committee (CHD 20) of the Bureau of Indian Standards (BIS) has issued a wide circulation draft titled “Solvent-Borne Epoxy Based Zinc Phosphate Primer (Two Pack) — Specification (Second Revision)”.
BIS invites stakeholders and industry experts to review the draft, which was released on 11 April 2026 under document number CHD 20 (34128) WC, and to provide feedback. Comments may be submitted until 12 June 2026.
Background
Solvent-borne epoxy zinc phosphate primer (two-pack) is an anti-corrosive coating used to protect metal in harsh environments. It combines an epoxy base with zinc phosphate pigment and a curing agent to form a durable, well-adhered film that resists moisture, chemicals, and corrosion.
Scope
This standard specifies requirements, sampling, and test methods for solvent-borne epoxy zinc phosphate primer used to protect and decorate prepared metal surfaces, including those on railway coaches, bridges, and locomotives.
Key modifications
This second revision aligns the standard with current market needs. The title has been updated to distinguish between solvent-borne products and water-borne primers, and new requirements have been included for characteristics such as viscosity, volatile organic compound (VOC) content, and pull-off adhesion.
The requirements for solvent-borne epoxy based zinc phosphate primer (two pack) are specified in the table below
|
Sl No.
|
Characteristic
|
Requirement
|
|
i)
|
Consistency
|
Smooth uniform and suitable for brush/spraying
|
|
ii)
|
Drying time, h, Max
a) Surface dry
b) Hard dry
c) Force dry, 70 ℃
|
3
8
30 minutes with 15 minutes flash off time at 70 ℃
|
|
iii)
|
Finish
|
Smooth, matt and egg shell flat
|
|
iv)
|
Colour
|
Off white/grey/ as per the choice of end user
|
|
v)
|
Dry film thickness per coat:
a) By brushing, micron
b) By spray, micron
|
60 ± 5
55 ± 5
|
|
vi)
|
Volume solids, percent
|
50 ± 5
|
|
vii)
|
Flexibility and adhesion:
a) Bend test (with 6.25 mm dia mandrel and type 1 apparatus)
b) Scratch hardness (1500 g)
|
No visible damage or detachment after
No such scratch as to show the bare metal
|
|
viii)
|
Flash point (for each component)
|
Not below 25 ℃
|
|
ix)
|
Resistance to humidity under condition of condensation and salt spray (Expose for 500 h):
a) Resistance to humidity at (60 ± 5) micron
b) Resistance to salt spray at (60 ± 5) micron
|
To pass the test
To pass the test
|
|
x)
|
Pot life, h, (27 ± 2) ℃, Min
|
4
|
|
xi)
|
Mass, in kg/10 litre
|
12.5 - 14.5
|
|
xii)
|
Keeping properties
|
Not less than one year from date of manufacturing
|
|
xiii)
|
Viscosity, KU, of mixed paint
|
±10 of registered sample or as agreed between supplier and purchaser
|
|
xiv)
|
Volatile organic compound, gm/litre, Max
|
500
|
|
xv)
|
Pull of adhesion, on system, 5 MPa, Min as system on 5 mm blasted panel
|
5
|
Packing and Marking
The material shall be packed in metal containers in accordance with the relevant standards, unless otherwise agreed. Each component must be free from defects such as gel, coarse particles, or impurities. Any settled material should be mixed to a uniform consistency before use.
Each container must be clearly marked with details such as product name, manufacturer, batch number, manufacturing date, volume, mixing instructions, shelf life, storage conditions, safety instructions, and cautionary warnings.
Products meeting this standard may also carry the BIS Certification Mark in accordance with applicable regulations.
