ASTM A90 Zinc Coating Mass Test

ASTM A90 test method determines the average weight of the zinc or zinc alloy coating over a defined region of iron or steel, which may then be used to calculate the average thickness. The test method's final results must be expressed in either inch-pound units or SI units.

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Overview
Scope, Applications, and Benefits
Test Process
Specifications
Instrumentation
Results and Deliverables

Overview

ASTM A90 specifies a test method for determining the mass of zinc coating on galvanized steel products. The test measures coating weight per unit area by removing the zinc layer and calculating the mass difference.

This method is widely used in industries such as construction, automotive, and infrastructure, where galvanized steel is used for corrosion protection. It ensures that zinc coatings meet required specifications for durability and service life.

Scope, Applications, and Benefits

Scope

ASTM A90 evaluates the mass of zinc coating on iron and steel articles by chemically stripping the coating and measuring weight loss. The test ensures compliance with coating thickness and uniformity requirements.

The test evaluates:

Zinc coating mass per unit area
Uniformity of coating distribution
Effectiveness of the galvanization process
Corrosion protection capability
Compliance with coating specifications

Applications

Galvanized steel sheets and structures
Construction and infrastructure materials
Automotive components
Fasteners and hardware
Transmission towers and poles
Industrial coated products

Benefits

Provides accurate measurement of coating mass
Ensures adequate corrosion protection
Supports quality control in galvanizing processes
Assists in material selection and specification
Enables comparison of coating performance

Test Process

Sample Preparation

Galvanized specimens are cleaned and prepared for testing.

Coating Removal

Zinc coating is chemically stripped using an appropriate solution.

Weight Measurement

Specimens are weighed before and after stripping.

Data Recording & Evaluation

Coating mass per unit area is calculated and evaluated against requirements.

Technical Specifications

Parameter	Details
Applicable Materials	Zinc-coated steel and iron
Specimen Area	~50 cm² to 100 cm²
Coating Mass Range	~50 g/m² to 600 g/m²
Stripping Solution	Acidic solution (e.g., inhibited HCl)
Measurement Accuracy	±1 g/m²
Measured Outputs	Coating mass (g/m²)

Instrumentation Used for Testing

Analytical balance (accuracy ±0.001 g)
Chemical stripping solutions and containers
Sample cutting tools
Drying oven
Protective laboratory equipment
Data recording system

Results and Deliverables

Zinc coating mass per unit area (g/m²)
Coating thickness estimation
Uniformity assessment of coating
Compliance with specification requirements
Test condition summary
ASTM compliance report

Why Choose Infinita Lab for ASTM A90?

Infinita Lab is a trusted USA-based testing laboratory offering ASTM A90 testing services across an extensive network of accredited facilities across the USA.

Infinita Lab is built to serve the full spectrum of modern testing needs—across industries, materials, and methodologies. Our advanced equipment and expert professionals deliver highly accurate and prompt test results, helping businesses achieve quality compliance and product reliability.

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Frequently Asked Questions

The ASTM A90 is a test method for determining the weight [mass] per unit area of zinc or zinc alloy coatings on a defined area of iron or steel by weighing before and after coating.

Zinc's most important role is to provide a barrier to protect steel against corrosion. The thickness and uniformity of the coating will influence this barrier effect.

The ASTM A90 test broadly applies zinc (galvanized) coatings. However, it can also be employed on other metallic coatings on iron and steel, such as aluminum, tin, or other protective coatings.

ASTM A90 evaluates coating mass per unit area and uniformity, ensuring zinc coatings meet specified requirements for durability and corrosion protection.

ASTM A90 evaluates coating mass under controlled conditions and may not fully represent coating performance in service environments affected by wear, corrosion, or environmental exposure factors.