Service life chart for hot-dip galvanized sheet In addition to The Coating Life Predictor, the books by Zhang10 and Porter11 are excellent sources for additional and more detailed information on the corrosion behaviour of zinc-coated steel, not only in the atmosphere but indoors, in … In most dry inland situations this can be infinitesimally slow, less than 1 micron per year, and unlike other coatings, a galvanized coating deteriorates in a linear fashion. The material categories are: Plate, Structural Shape, Strip and Bar. Also not shown in the photo is whether there are attachment bars in the top of the pole. Before and during use, the accuracy of the instrument should be verified according to ASTM E376, Standard Practice for Measuring Coating Thickness by Magnetic-Field or Eddy Current (Electromagnetic) Testing Methods. It does indeed pay to know your microns. The Galvanized Sheet Gauge is based on the U.S. Standard Gauge. Therefore, the best representation of coating thickness is obtained by averaging a series of measurements as per ASTM A123-02. There is no set formula except that the areas must be nominally equal. HOT DIP GALVANIZED STEEL, known as ZINCGRIP® Steel, is continuously coated on both sides with a zinc coating. This is especially true for fabricated items as discussed later. If structural shapes greater than 5/8 inches in thickness are being galvanized, Table 1 indicates that the coating grade is 100. 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. And what does ‘85 microns’, actually look like? How this microscopic coating then weathers is predictable but complex and fluctuates with atmospheric conditions. Use of high silicon steel enables a still thicker coating of 200 μm to be specified. 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. There are two different methods used to measure the coating thickness of hot-dip galvanized steel: a magnetic thickness gauge and optical microscopy. Coating Weight Coating Thickness to reach 1 oz/ft2 Hot-dip galvanizing (batch or continuous), electroplating, zinc plating 1.7 mils (43 µm) Metallizing (zinc spraying) 1.9 mils (48 µm) Mechanical plating 2.2 mils (55 µm) Zinc-rich paint 3-6 mils (75-150 µm) The countdown has begun to the annual GAGAs - Galvanizers Association Galvanizing Awards... Privacy Conclusion – Achieving the proper thickness of hot-dip galvanizing is critical in assuring it achieves its expected performance. A minimum of 5 spot readings are obtained in each specimen area. Any of the three  averages may be one coating grade below the requirement provided the grand average is the coating grade requirement. Galvanized Sheets - Continental Steel & Tube Company. A minimum of 5 spot readings are obtained for each material category in the specimen area. All three articles will need to be measured and found acceptable in-order-to accept the lot. Wear resistance. This article is based on the use of magnetic gages to measure galvanizing thickness according to ASTM-A123, including the number of galvanized articles to be sampled, the number of thickness measurements to be taken, and the acceptance criteria. In addition to steel thickness, the composition of the steel alloy itself is also relevant. The definitions are provided in a logical order in which the terms are used, rather than alphabetical. Figure 1. The readings in each area are averaged to obtain 3 averages per article. Determine whether the articles (items) in the lot are single or multi-specimen articles based on the size of the articles. The specifications for hot-dip galvanizing do not set a maximum coating thickness, so there is no limit on the thickness of the hot-dip galvanized coating. A gauge conversion chart can be used to determine the actual thickness of sheet metal in inches or millimeters. per sq.ft. For one-side or differential coating, please inquire. The definition of a lot is flexible in that it can be a shift’s production, a day’s production, or a truck load, but it generally consists of articles of the same size and shape. In other words, the two sizes are sampled separately. For multi-specimen articles, divide each article into thirds to select the specimens for measurement (3 specimens for each article). 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. Prevent product failure by ensuring coating thickness and uniformity of … 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. For clarity galvanized, Table 1 indicates that the galvanizing is 705 grams/square meter or ounces/square. 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