ASTM A90 Weight of Coating on Iron and Steel Articles with Zinc or Zinc-Alloy Coatings

Get Certified ASTM A90 Testing for Reliable Zinc Coating Weight Measurement

ASTM A90 establishes the amount of zinc or zinc-alloy coating on iron and steel products. This standard allows engineers to assess coating conformance and corrosion protection. The coating mass is a good indicator of the available protective coating since zinc is sacrificial to iron and steel. The results can also be used for quality control, material comparison, and product acceptance.

• Material type: Iron and steel articles with zinc or zinc-alloy coatings.
• Purpose: Determination and evaluation of zinc or zinc-alloy coating weight or mass.
• Property measured: Average coating weight or mass per unit area.
• Method: The test involves cleaning and weighing the specimen, chemically removing the zinc or zinc-alloy coating, and reweighing the specimen to determine the mass difference.
• Result: Coating weight or mass is reported as mass per unit area.
• Units: Results are reported in g/m² for SI units or oz/ft² for inch-pound units.
• Sheet products: The method can determine total coating weight on both sides or coating weight on an individual side when applicable.
• Thickness evaluation: Engineers can calculate average coating thickness from the measured coating mass when the coating density is known.
• Applications: Galvanized steel quality control, coating verification, material specification compliance, manufacturing evaluation, and corrosion-protection assessment.

What are the Uses of ASTM A90 Testing?

ASTM A90 testing is for the average weight or mass of zinc and zinc-alloy coatings on iron and steel products. This lets engineers compare measured results with applicable coating requirements and product specifications. The test can also be used for corrosion-protection evaluation, manufacturing quality control, material verification, and product acceptance. The ASTM A90 standard-

• Measures the weight of the zinc or zinc-alloy coating.
• Facilitates conformance evaluation of coating.
• Helps evaluate corrosion protection.
• Checks the amount of coating on steel products.
• Helps improve the production quality control process.
• Assists in material comparison.
• Delivers information for engineering assessment.
• Complies with acceptance criteria for products.

Which materials can be tested under ASTM A90?

ASTM A90 is applicable to iron and steel sheets, wire, and other articles with zinc or zinc alloy coatings. It is applicable to zinc-5% aluminum, zinc-aluminum-magnesium, and 55% aluminum-zinc coatings within its scope of application. When applicable, analysts can measure the total coating weight of both sides of the sheet product or measure each side individually.

Why is ASTM A90 Important?

ASTM A90 is significant because it provides a standard method to measure the weight of the coating on coated iron and steel products. As zinc is a sacrificial protection coating, the thickness of the coating may be correlated with the protection level available. Hence, the results can be used by engineers to compare products having the specified coating class and applicable material requirement.

ASTM A90 Testing Process and Data Collection

The technical staff initially choose representative coated specimens based on the product requirements. Afterward, they prepare and weigh each specimen and remove the zinc or zinc-alloy coating. Then operators take off the coating and prepare the remaining specimen for weighing. Finally, the mass difference and coated area are used to calculate the average coating weight. The engineers may report the coating weight on both sides or the coating weight on each side if necessary for sheet products.

Common Challenges and Troubleshooting

Proper specimen preparation, complete coating removal, and reliable mass measurements are all important for accurate ASTM A90 results, as are representative samples. Thus, it is important that technicians check the condition of specimens and weighing equipment prior to testing. Coating-removal procedures should also be used, as applicable, to prevent incomplete coating removal and to avoid any unnecessary effects on the base metal. Lastly, analysts should check the area of the specimen and calculations before reporting the results.

• The laboratory reports coating mass in g/m² or oz/ft² for inch-pound units, as applicable.
• The technician records coating mass for the tested surface or both surfaces of the sheet, depending on the applicable measurement and reporting requirements.
• The analyst calculates coating mass from the difference between the specimen masses before and after coating removal and the corresponding surface area.
• Engineers report the average coating mass and compare it with the applicable material specification requirements for evaluation.
• Engineers use the average coating mass to calculate the average coating thickness when the coating density is known.

Link to ASTM A90