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BIS Certification for Hot-Dip Zinc Coating on Structural Steel and Allied Products IS 4759:1996

Corrosion is one of the most persistent threats to the integrity and longevity of steel structures. In industries like construction, transportation, energy, and manufacturing, protecting steel from rust is essential not just for durability but also for safety and cost-effectiveness. Hot-dip galvanizing, a widely accepted method of corrosion protection, plays a crucial role in addressing this challenge.

The Bureau of Indian Standards (BIS), through its standard IS 4759:1996, regulates the hot-dip zinc coating process for structural steel and other allied products in India. This standard sets comprehensive guidelines for quality, testing, and application of zinc coatings to ensure that galvanized steel products meet the requirements for performance, durability, and safety.

What Is Hot-Dip Zinc Coating?

Hot-dip galvanizing is a metallurgical process where steel or iron products are immersed in molten zinc, resulting in a tightly bonded, corrosion-resistant coating. This process forms multiple layers of zinc-iron alloy between the base steel and the outer layer of pure zinc. The result is a highly durable protective barrier that shields the steel from environmental elements such as moisture, oxygen, and pollutants.

This method is particularly suited for structural steel used in bridges, towers, pipelines, building frameworks, power transmission structures, railways, and a wide range of industrial applications exposed to weather or corrosive environments.

IS 4759:1996 – An Overview

Indian Standard IS 4759:1996, titled “Hot-Dip Zinc Coatings on Structural Steel and Other Allied Products – Specification”, lays out detailed provisions for the galvanizing process, from material selection to testing criteria. The standard applies to a variety of products, including structural shapes, plates, pipes, and fabricated steel items.

Key Aspects Covered:

● Quality of Zinc Used: The zinc used in the galvanizing bath must conform to the required purity standards to ensure consistent and defect-free coatings.

● Galvanizing Bath Composition: The bath typically contains zinc heated to approximately 450°C. Alloying elements such as aluminum or lead may be added in controlled proportions to enhance fluidity and coating adherence.

● General Coating Requirements: The zinc coating must be uniform, continuous, and free from defects such as lumps, blisters, acid spots, or uncoated patches.

● Minimum Coating Mass: The standard specifies the minimum average mass of zinc coating (expressed in gm/m²) based on the thickness and type of the steel product.

● Surface Preparation: Before galvanizing, the steel must be cleaned of rust, scale, oil, paint, and other contaminants to ensure proper metallurgical bonding of the zinc layer.

● Purchaser’s Information: IS 4759 also outlines what information the purchaser must provide, including the type of product, applicable drawings, surface condition requirements, and any special instructions.

Importance of BIS Certification

Obtaining BIS certification under IS 4759:1996 is mandatory for manufacturers and suppliers who wish to market hot-dip galvanized steel products in India under regulatory compliance. Certification ensures that:

● The coating process meets defined national quality standards.

● The galvanized product is suitable for long-term use in critical infrastructure and industrial settings.

● The end users, contractors, and public agencies are assured of safety, durability, and value.

Moreover, certified products are often a prerequisite in government tenders and large infrastructure projects, making BIS certification commercially vital.

Testing and Quality Assurance

To ensure that galvanized products meet the requirements of IS 4759:1996, BIS mandates a series of quality tests. These tests are typically conducted during the certification process and at regular intervals thereafter.

Core Tests Include:

● Mass of Zinc Coating: Measured using a gravimetric or magnetic method to ensure the zinc layer meets the required thickness.

● Freedom from Defects: Visual inspection is carried out to confirm that the surface is free from cracks, flaking, bare spots, ash inclusions, or excessive runs.

● Uniformity of Zinc Coating: The uniformity of coating is tested using the copper sulphate test, which simulates prolonged exposure to a corrosive environment. A consistent coating will resist attack over multiple cycles.

● Adhesion of Galvanized Coating: The coating is evaluated for its ability to adhere to the steel substrate, ensuring that it will not peel, blister, or delaminate under normal service conditions.

All testing is carried out at BIS-approved laboratories or in-house facilities certified under the BIS Laboratory Recognition Scheme.

BIS Certification Process for Manufacturers

Manufacturers seeking BIS certification under IS 4759:1996 must undergo the following process:

Application Submission: Provide technical documents, manufacturing details, and process flow related to galvanizing.

Product Sampling & Testing: Samples are taken and tested as per IS 4759 specifications.

Factory Audit: BIS officials inspect the facility for quality control practices, production capabilities, and testing infrastructure.

Grant of Certification: Upon successful evaluation, BIS grants a license to use the ISI Mark on compliant products.

Surveillance & Renewal: Periodic factory audits and retesting ensure continuous compliance.

To Know The Process in Detail, Please Visit:

BIS ISI Mark Certification for Domestic Manufactures
BIS ISI Mark Certification for Foreign Manufactures

Under BIS Registration Products ISI and CRS

BIS CRS Registration For IT Products List
BIS ISI Mark Certification For ISI Products List

Documents Required for BIS Certification

To apply for BIS certification, manufacturers need to submit the following documents:
●  Application form
●  Manufacturing process details
●  Quality control plan
●  Test reports from BIS-approved laboratories
●  Factory layout and equipment details
●  Proof of business registration
●  Product specifications and technical details
●  Declaration of conformity to Indian standards
Additionally, manufacturers may be required to provide proof of compliance with environmental and safety regulations, depending on the specific type of product being certified.

BIS ISI Mark Certification Costing And Timeline

Conclusion

As India rapidly expands its infrastructure footprint, the demand for durable and corrosion-resistant steel products is growing. Hot-dip galvanized steel, regulated under IS 4759:1996, plays a vital role in meeting this need. BIS certification ensures that the products used in critical projects—from highways to power grids—are not only structurally sound but also built to last.

For manufacturers and suppliers, compliance with IS 4759 is not just about meeting a regulatory requirement—it's about demonstrating commitment to quality, safety, and performance.