Sudha Speciality Chemicals Private Limited | Manufacturer of water treatment and specialty chemicals

  • Call Us: +91 33 40043265
    info@sudhaind.com

Get a Quote

Passivation of Galvanised and Galvalume Steel Strip: Preventing White Rust

Passivation is a surface treatment process that applies a clear chromium layer onto freshly galvanised and Galvalume coated steel strips. Utilizing high-performance metal passivation chemicals, this protective chemical film prevents white rust, storage stains, and bronzing effects that downgrade surface quality during transit. For continuous coil coating lines, a reliable passivation chemical is essential to protect the finish and reduce customer rejections.

What is SUPASS Passivation Chemical?

SUPASS is a proprietary, highly acidic, reddish-green liquid anti-corrosion passivation chemical manufactured by Sudha Speciality Chemicals. It uses both hexavalent and trivalent chromium chemistry to deposit a self-healing protective film over zinc alloys, serving as a comprehensive passivation solution for metal surface treatment. 

While operations handling different metal substrates might require a dedicated stainless steel passivation chemical, SUPASS is designed specifically for continuous galvanised strips and works seamlessly with conventional dip squeeze, spray squeeze, Roll Coater, and Chem Coater applications.

What are the Benefits of SUPASS for Coil Operations?

When moisture reaches unprotected zinc, white rust forms rapidly. SUPASS resists this corrosive attack while keeping operational overhead low.

  • ● Superior Corrosion Resistance: Delivers 96 hours of salt spray resistance and self-healing hexavalent chrome protection against white rust and bronzing.
  • ● Energy Efficient Processing: Operates effectively at room temperature (20 to 45 degrees Celsius), eliminating the need to heat or cool the bath solution.
  • ● Water and Space Conservation: Requires no post-rinse system, freeing up factory floor space and reducing water consumption.
  • ● Simplified Waste Management: Contains no chelating agents, making effluent treatment straightforward and compliant.

Technical Specifications and Operating Parameters

To achieve optimal coating weights and superior salt spray resistance, plant engineers must maintain the following operational parameters.

Parameter

Recommended Range

Application Temperature

20 to 45 degrees Celsius (Room Temp)

Total Chrome Content

Approximately 60.0 g/L

Contact Time

1 to 2 seconds

Peak Metal Temperature (PMT)

55 to 75 degrees Celsius

Squeeze Roll Pressure

3 to 6 kg/cm2

Coating Weight

15 to 25 mg/m2 per side

How to Maintain a Passivation Bath for Maximum Yield

For line managers focused on cost control, SUPASS delivers highly predictable yield and maintenance cycles. Follow these standard guidelines for optimal bath life:

  • ●  Control Chemical Consumption: When properly calibrated, chemical consumption is approximately 75 ml (+/- 2 ml) per 100 square meters of steel strip.
  • ●  Use Correct Equipment: Squeeze rolls must be constructed of chromic acid-resistant rubber like Hypalon. Holding tanks should utilize Type 316 stainless steel or PVC linings.
  • ●  Ensure Rapid Drying: The treated strip must be dried rapidly at a PMT of 55 to 75 degrees Celsius. Air movement must remove water without physically disturbing the wet film.
  • ●  Prevent Zinc Contamination: Maintain a short reaction distance to the squeeze rolls (maximum 1.0 meter) and keep bath temperatures below 40 degrees Celsius. Zinc contamination must stay below 2000 ppm and never exceed 3000 ppm to avoid turbidity.

Safe Handling and Effluent Disposal Guidelines

Because SUPASS contains hexavalent chromium, strict safety and disposal protocols are required. Hexavalent chromium waste is managed through chemical reduction using Sodium Bisulphite. The supernatant liquid can then be discharged once it meets local regulatory standards for trivalent and hexavalent content. Workers must wear standard personal protective equipment, including rubber gloves, aprons, boots, and face shields, to prevent skin and eye contact.

Why Collaborate with Sudha Speciality Chemicals

Sudha Speciality Chemicals Private Limited, a passivation chemical manufacturer, is a Kolkata-based company established in 2002. Our technical team provides end-to-end support for bath make-up, routine maintenance, and analytical control to ensure your galvanising line runs smoothly.

Contact us today to discuss passivation solutions for your continuous coil line:

Scroll to Top