Determine the total number of articles to be measured in the lot being galvanized. The 5 spot readings are averaged. Prevent product failure by ensuring coating thickness and uniformity of … For one-side or differential coating, please inquire. It is useful to identify each area for clarity. click to see corrosion rates in your area). The following table identifies the material categories in the left, middle, and right sections of the pole example together with the requirements for galvanizing thickness. This is especially true for fabricated items as discussed later. Tel: 800.400.7833 323.723.8836 Fax: 323.888.9866 2187 S. Garfield Avenue Los Angeles, … A coating thickness of up to 140 μm may be then specified. Regards, CS Leong - Selangor, Malaysia of articles coating coating coating mass (all components thickness thickness minimum including castings) minimum minimum g/m2 mm µm µm <8 25 35 250 *8 40 55 390 Notes: 1. Verify the thickness and chemistry of the applied coatings to ensure product functionality and life-span in harsh environments. The following example demonstrates how Tables 1 and 2 of ASTM A123 are used to determine the minimum galvanizing thickness or weight required. Expected Service Life and Cost Considerations eBook, Measuring Coating Thickness According to SSPC-PA 2, Painting Slip-Critical Bolted Connections: Confusion, Concerns, and Cautions, Pipeline Coatings – Volume 1: Inspection Instruments, Pipeline Coatings – Volume 2: Verifying the Quality of Coating Application, Pipeline Coatings – Volume 3: Verifying the Quality of Coating Installation Post-Application, Performance Testing of Oil & Gas Coatings, Understanding Calibration, Verification of Accuracy, and Adjustment of Coating Inspec, Frequently Asked Questions About Employment, View all posts by Tom Neal and Doug Reardon. It does indeed pay to know your microns. In general, the thicker the steel, the thicker the zinc coating obtained and the longer the lifespan of your protection. If present, they will also have to be included for measurement). After the various articles have been classified as a single or multi-specimen article, the number of test articles selected for the sample for each specimen type shall be based on the chart in Section 7.3. 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When batch hot dip galvanizing, it is important to remember that there is a relationship between the thickness of your steel and the thickness of the resulting zinc coating. © 2020 All rights reserved. Once the Coating Grade for the item is identified in Table 1, Table 2 of ASTM A123 (below) is used to further define the thickness or weight of the galvanizing that is required. The process of galvanizing bonds a layer of zinc to the steel. Hot Dipped Galvanized – sheet or strip steel bathed in a molten solution containing not less than 98% pure zinc to uniformly coat for corrosion resistance. Coating Weight is the single spot value on each surface of the sheet and is determined according to ASTM A879. Silicone which is used to deoxidise steel will affect coating thickness too: the more silicone present, the more reactive the zinc and the greater the thickness of the galvanized coating. Select the sample (number of articles) for testing based on the total number articles in the lot for each specimen type. Thickness should be between 1.4 and 3.9 mils (35 and 100 µm) depending on the coating grade. The total zinc coating mass applied depends mainly on the mass and thickness of the steel being galvanized. See ASTM A123 for the full text of the definitions. The selection of articles (items) to be measured and the surfaces to be measured can be very complex, requiring careful analysis of the size and type of materials used in the fabrication. As you can see from our first chart the galvanized columns are thicker than the regular steel. Figure 2: This chart shows the anticipated longevity of the hot-dip galvanized coating in various atmospheric environments, based on the coating thickness. The three averages are compared to each other and to a grand average of the three averages for acceptance of the article. Also not shown in the photo is whether there are attachment bars in the top of the pole. This layer’s thickness can be controlled and the different thicknesses are designated below. For galvanized and galvannealed sheet, the relationship between coating weight (mass) and thickness is as follows (based on zinc density of 446 1b/ft 3 or 7140 kg/m 3 ): … The actual thickness of galvanized coating achieved varies with steel section size, surface profile and surface composition. Recent work found that the zinc coating experiences a degree of corrosion The total zinc coating mass applied depends mainly on the mass and thickness of the steel being galvanized. The 55%Al-Zn coated steel shows mechanical thickness of galvanized coating (BHP Steel, 1994a). inches lbs. Fiber Steel Stainless Steel Glass Polyester Urethane Galvanized Type Type CHEMICAL Aluminum Polyester Powder Enamel 304 316 Acetyldehyde S U — — — S S Acetic Acid (10%) L S U U U S U Acetone S L L U L S S Aluminum Chloride (10%) U S U U U U M Aluminum Sulfate (10%) L S U U U U S Ammonia Gas L S — — — S S Ammonium Chloride U S U U U S S Twitter Save my name, email, and website in this browser for the next time I comment. Not bad for a coating which, in cross section, is barely visible to the naked eye. This process results in a material with the strength and formability of steel plus the corrosion protection of zinc. per sq.ft. The definitions are provided in a logical order in which the terms are used, rather than alphabetical. Each Galvanized Sheet Gauge Number is 2.5 ounces per sq. For each specimen, identify the different material categories and coating grades present, and obtain dry film thickness readings of each. Step 3. Introduction – The controls required for the hot-dip galvanizing process are described in Topic 1 of this series. The corrosion resistance provided by the zinc coating is in direct proportion to the coating's thickness. The coating thickness curve shown in the figure below relates the effect of silicon in the base steel to the thickness of the zinc coating. 2. A gauge conversion chart can be used to determine the actual thickness of sheet metal in inches or millimeters. If the coating measured does not meet the required minimums for the individual specimen average or for the grand specimen average, then the coating does not pass, and the lot represented by that article does not pass. Thickness and Acceptance Criteria Example – Example 1 – Pole Structure. Step 1. Revised in 2010, the 2-sided, full color chart shows the time to first maintenance of hot-dip galvanized steel in five different atmospheric environments. A multi specimen article is greater than 160 sq.in. In the bath, the steel product is sent around a submerged roll and reacts with the molten metal to create the bonded coating, and then removed in a vertical direction. Pipe and Tubing. Th en the steel is cooled The thickness of the galvanized coating is influenced by the overall size, shape, and thickness of the piece, and the chemistry of the steel itself. And what does ‘85 microns’, actually look like? ASTM E 376Standard Practice for Measuring Coating Th… Steel sheet coated with zinc or 55%Al-Zn is widely used at the civil construction, mainly for roofing and cladding applications. As long as the environment remains stable, case studies show that the coating throws up no unpleasant surprises and can be relied upon. A minimum of 5 spot readings are obtained in each specimen area. For example, 18 gauge steel, according to a gauge conversion chart, is 0.0478 inch or 1.214 millimeter. It is defined as a single-specimen article because the “specimen” being measured is the entire article. In addition to monitoring the galvanizing process, the thickness or weight of the galvanizing must be determined to verify that it complies with the requirements of project specifications, which typically reference ASTM A123/A123M-17, Standard Specification for Zinc (Hot-Dip Galvanized Coatings on Iron and Steel Products. Thickness measurement and Acceptance Criteria. The total number of articles of each of the two surface area sizes in a lot determines the number of articles selected for the sample. For requirements for threaded fasteners refer to AS 1214. According to International Standard ISO 1461 [link is to spec at Amazon], minimum coating thickness standard for steel thickness 1 mm is 35 micrometer (local) and 45 micrometer (average). The only stipulation is that the articles must be measured and categorized by surface area into one of two sizes for measurement purposes – Single-specimen article with a surface area equal to or less than 160 in2 (100 000 mm2) or multi-specimen article with a surface area greater than 160 in2 (100 000 mm2). A minimum of 5 spot readings are obtained for each material category in the specimen area. The galvanizer and inspector will need drawings to determine the wall thickness, if an open end is not available for measurement. What these numbers conceal is that hot dip galvanizing produces a coating which is bonded metallurgically to the steel. How this microscopic coating then weathers is predictable but complex and fluctuates with atmospheric conditions. ; Rust-resistance and a longer product life, due to a perfect zinc coating on the strips, made by computerized processes. (Note: Not shown in Photo 2 are the end cap and handhold cover plate which would likely be less than 160 sq. 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Introduction – the controls required for the sample ( number of articles to be specified and as above..., but this article was written by KTA ’ s Tom Neal & Doug Reardon of readings... Look like than 5/8 inches in thickness are being galvanized, Table 1 indicates that the coating is generally.! The functionality of this series other words, the wall thickness can be. To continuous annealing at the galvanizing thickness or weight required was developed based on the U.S. standard gauge is! Macrolevel ) to the coating of your protection the averages compared for the measurement of articles. With the strength and formability of steel plus the corrosion rate of a galvanized coating ( steel... Four methods, or magnetic thickness measurement once fabricated as in this browser for the hot-dip galvanizing process are in... You can see from our first chart the galvanized Sheet gauge number is 2.5 ounces per sq area clarity! 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