If I galvanize to ASTM A123 or A153, will I meet the requirements of ISO 1461?
ISO 1461, Hot-dip galvanized coatings on fabricated iron and steel articles Specifications and test methods is produced by the International Organization for Standardization (ISO) as an industry standard for galvanizing. The standard holds requirements for hot-dip galvanized steel comparable to those found in both ASTM A123, Standard Specification for Zinc (Hot-Dip Galvanized) Coatings on Iron and Steel Products, and ASTM A153, Standard Specification for Zinc Coating (Hot-Dip) on Iron and Steel Hardware. North American specifiers and galvanizers typically use ASTM A123 and A153 for steel products and fasteners to be hot-dip galvanized. However, ISO 1461 which standardizes the European galvanizing industry both large structural pieces and centrifuged hardware is also sometimes used in Canada, the United States, and Mexico.
If a customer wishes to use ISO 1461 on their project, galvanizers need to know what the requirements of the standard are and if they can meet them. As North American galvanizers, the question becomes, If I galvanize the steel to ASTM A123, will I meet the requirements of ISO 1461? The simple answer: Yes, if the requirements of ASTM A123 are met, then the requirements of ISO 1461 will more than likely also be met. However, galvanizers should be aware of some small differences between the two specifications if they are going to be using ISO 1461 frequently. These differences exist within the testing methods of the two standards and slight overlaps in coating thickness requirements.
The ASTM and ISO standards share similar testing requirements for coating thickness. Both A123 and 1461 use a magnetic or electronic coating thickness gauge as the primary means for determining mean coating thickness of hot-dip galvanized steel. Both standards also rely on the weigh-strip-weigh procedure (referred to as the gravimetric method in ISO 1461) as an alternate method of determining coating thickness when magnetic gauges are not appropriate or as a referee method.
The sampling requirements are extremely similar between the standards. Each standard requires a certain number of test articles or specimens to be randomly pulled from a lot and then be tested for coating thickness. The number of articles or specimens to be pulled from the lot is determined by ISO 1461 Table 1, which is exactly the same as the charts found in ASTM A123 section 7.3 and ASTM A153 section 6.2. However, a difference lies in how the average coating thickness is determined after the lot is broken down into this control sample.
ISO 1461 requires that after a control sample is produced from the lot, the articles need to be further broken down into reference areas. Each reference area uses the average of five measurements within a small area to determine an average. These averages are used to determine the mean coating thickness of the entire lot. In contrast, ASTM A123 calls for the control sample to be made up of specimens. Once the specimens are determined, they need not be broken down any further. A123 also calls for five measurements within each specimen, but these are to be widely dispersed throughout the volume of the specimen rather than spaced close together. These may seem like small differences that are probably negligible for you and your customer but may be important to know if a dispute does arise.
More differences between the standards are present in the minimum average thickness requirements. These differences may be considered negligible, and galvanizers will most likely meet the requirements of ISO 1461 if they galvanized to A123. However, there may be a reason to know the differences between the two to the letter of the law. The table below helps point out these subtle differences. The table assumes steel is being galvanized according to the thicknesses in the left-hand column. This column uses the standard units of mm found in ISO 1461 but can be converted to imperial units. The table then gives the requirements of ISO 1461, and the thickness of steels whose A123 requirements overlap. Notice the ASTM requirements for coating thickness on wire never meet the ISO standards.
As has been said previously, the differences between ISO 1461 and the combination of ASTM A123 and A153 are rather small. If steel is galvanized in accordance with ASTM A123 or A153, it will more than likely meet the requirements of ISO 1461. The information above is meant to be nit-picky and point out the small differences.
ISO 1461 Table 3
|ASTM A123 will meet requirements if:|
|Steel thicker than 6mm||85||
|Steel thicker than 3mm and up to 6mm||70||
|Steel thicker than 1.5mm and up to 3mm||55||
|Steel thinner than 1.5mm||45||