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IS 11817:1986 is the Indian Standard (BIS) for zinc coatings for steel structures - hot dip galvanizing - code of practice. This standard provides a code of practice for the hot-dip galvanizing of steel structures. It specifies requirements for the base steel material, the galvanizing process including surface preparation and zinc bath composition, and the properties, inspection, and testing of the final zinc coating.
Lays down recommendations for hot dip galvanizing of fabricated steel structures and components, such as metal fencing and crash barriers, for corrosion protection.
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! This standard has been withdrawn. For current practice, refer to IS 2629 (Recommended practice for hot-dip galvanizing) and IS 4759 (Specification for hot-dip zinc coatings).
! Proper surface preparation (degreasing, pickling, fluxing) is absolutely critical to achieve good adhesion and a uniform coating.
! Be aware of potential distortion of thin or complex fabricated parts due to the high temperature of the molten zinc bath.
ISO 1461:2022ISO (International Organization for Standardization), Switzerland
HighCurrent
Hot dip galvanized coatings on fabricated iron and steel articles — Specifications and test methods
Both standards cover the requirements and process for hot-dip galvanizing of fabricated steel items.
ASTM A123/A123M-17ASTM International, USA
HighCurrent
Standard Specification for Zinc (Hot-Dip Galvanized) Coatings on Iron and Steel Products
Specifies requirements for hot-dip galvanized coatings on structural steel shapes, plates, bars, and strips.
BS EN ISO 1461:2022BSI (British Standards Institution), UK / CEN (European Committee for Standardization), Europe
HighCurrent
Hot dip galvanized coatings on fabricated iron and steel articles — Specifications and test methods
The European and British adoption of ISO 1461, making it the primary standard for those regions.
AS/NZS 4680:2006Standards Australia / Standards New Zealand
HighCurrent
Hot-dip galvanized (zinc) coatings on fabricated ferrous articles
The Australian and New Zealand standard, largely based on ISO 1461 with some regional modifications.
Key Differences
≠IS 11817 is a 'Code of Practice' focusing on the process, whereas modern standards like ISO 1461 are 'Specifications' focused on the final product requirements and testing, offering more quantifiable acceptance criteria.
≠The Indian standard specifies coating requirements by mass (e.g., g/m²). International standards primarily use thickness (µm) and provide more detailed tables based on steel section thickness, including requirements for both 'local' and 'mean' coating thickness.
≠Modern standards like ISO 1461 provide very specific quantitative limits for the size of uncoated areas that can be repaired (e.g., not exceeding 0.5% of total area) and the required thickness of the repair coating (e.g., min. 100 µm). IS 11817 is less specific, referring only to 'small bare spots'.
≠IS 11817:1986 has less emphasis on the influence of steel chemistry (Silicon and Phosphorus content) on the final coating thickness and appearance, a topic that is well-defined and discussed in the informative annexes of ISO 1461 and ASTM A123.
Key Similarities
≈All standards are fundamentally based on the same process: thorough surface preparation (degreasing, acid pickling, fluxing) followed by immersion in a bath of molten zinc.
≈All standards recognize the primary purpose of the coating is to provide long-term corrosion protection to the steel through both barrier and sacrificial (cathodic) mechanisms.
≈The requirement for good coating adhesion is a common principle. The test method, typically involving attempting to lift the coating with a stout knife, is conceptually identical across all standards.
≈All standards mandate a minimum coating mass/thickness as the primary measure of quality and expected service life, although the specific values and categorization may differ.
Parameter Comparison
Parameter
IS Value
International
Source
Coating Requirement (Steel >5-6mm thick)
Minimum average mass of 610 g/m² (refers to IS 2629)
Minimum mean thickness of 85 µm (approx. 612 g/m²)
ISO 1461:2022
Local vs. Mean Thickness
Specifies only a single average mass requirement.
Specifies both a 'mean' thickness (e.g., 85 µm) and a 'local' minimum thickness (e.g., 70 µm).
ISO 1461:2022
Maximum Repairable Bare Area
Not quantitatively defined; refers to 'small bare spots'.
Total area for renovation shall not exceed 0.5% of the total surface area.
ISO 1461:2022
Required Thickness of Repair Coating
Not specified. States repair can be done by painting with zinc-rich paint.
Minimum thickness of 100 µm, regardless of the repair method used.
ISO 1461:2022
Zinc Bath Purity
Refers to IS 209 (e.g., Grade Zn 98.5), minimum 98.5% Zinc.
The molten metal in the bath shall contain not less than 98.0% zinc by mass.
ISO 1461:2022
Adhesion Test Method
Prying with a stout knife to attempt to lift the coating (as per IS 2633).
A stout knife is used to attempt to lift the coating; it should not flake off.
ASTM A123/A123M-17
⚠ Verify details from original standards before use
Key Values5
Quick Reference Values
Minimum zinc purity for galvanizing bath98.5% by mass
Typical zinc bath temperature445 to 465 °C
Minimum average coating mass for steel > 5mm thick610 g/m²
Minimum average coating thickness equivalent for steel > 5mm thick86 µm
Minimum individual coating mass for steel > 5mm thick460 g/m²