ASTM A924 General Requirements for Steel Sheet, Metallic-Coated by the Hot-Dip Process

Get Certified ASTM A924 Testing

The ASTM A924 evaluation provides steel producers, coating manufacturers, suppliers, fabricators, engineers, inspectors, and quality-control professionals with a means to assure that hot-dip metallic-coated steel sheet meets the general requirements of the appropriate ASTM A924. The evaluation includes evaluation of material, coating, dimensions, mechanical properties, and quality as per the material product specification. Qualified technicians can inspect the steel sheet, measure the size and coating properties, and conduct or supervise mechanical and chemical tests. 

• Material Type: Metal-coated steel sheet (Metal Coated Hot Dip Steel Sheet). 
• Coating: Metallic coatings, applied by immersing in a molten coating bath. 
• Chemical Properties: Chemical requirements of the applicable product specification. Coating properties, coating designation, adhesion, and coating measurements. Thickness, width, length, shape, flatness, and applicable dimensional tolerances. 
• Workmanship: Defects and surface condition that may impact product suitability. 
• Testing: Mechanical, coating, dimensional, and other tests as specified in the applicable product specification. 
• Inspection and Sampling: General provisions for sampling, testing, inspection, rejection, retesting, and certification. Applications: Applies to the standardized purchasing, manufacturing, inspection, and acceptance of hot-dip metallic-coated steel sheet. 

What are the uses of ASTM A924?

ASTM A924 offers standardized criteria and testing procedures for hot-dip metallic-coated steel sheet for various product specifications. It facilitates the delivery of consistent quality, coating performance, dimensions, and testing from the manufacturer to the purchaser. Common uses include:

• Material Verification: Verification of the steel sheet to ensure the steel sheet conforms to the applicable grade and product requirements. 
• Coating Evaluation: Determination of the qualities of the metallic coating and coating designation. 
• Dimensional Inspection:  Checking thickness, width, length, flatness, and applicable tolerances. 
• Mechanical Testing: Testing tensile or other mechanical properties if necessary as per the applicable product specification. 
• Quality Control: Control of consistency of production and finished sheet quality. 
• Purchasing and Acceptance: Providing common requirements for supplier and purchaser evaluation. 
• Manufacturing Control: Assisting in consistent hot-dip coating and steel sheet manufacturing. 
• Certification: Providing information for material certification and inspection documents. 

Which Materials Can Be Tested According to ASTM A924?

ASTM A924 applies to metallic-coated steel sheet made by the hot-dip process. The coating metal and steel grade will vary depending on the applicable product specification that is used with ASTM A924. The specification thus covers a range of metallic-coated steel sheet products and not any one particular steel grade. Materials may include:

• Zinc-Coated Steel Sheet: Steel sheet that is hot-dip zinc-coated. 
• Aluminum-Coated Steel Sheet: Steel sheet coated by the applicable product specification with the coating of aluminum. 
• Zinc-Aluminium-Coated Steel Sheet: Steel sheets of applicable zinc-aluminum metallic coatings. 
• Aluminum-Zinc-Coated Steel Sheet: Steel sheet hot-dipped with the appropriate ASTM product specification. 
• Other Metallic-Coated Steel Sheet: Products that have ASTM specifications that reference ASTM A924 for general requirements. The composition of the coating, steel grade, coating designation, and mechanical requirements must always be taken from the corresponding product specification.

Why is ASTM A924 important?

ASTM A924 is significant because hot-dip metallic-coated steel sheet has to meet requirements for both the steel and the coat. Chemical composition, mechanical properties, coating attributes, sizes, and surface condition of steel may vary and can impact fabrication, corrosion resistance, aesthetics, and service performance. The specification offers a consistent set of rules for inspection and acceptance, but individual product standards offer some rules that are specific to certain steel grades and coatings. This allows ASTM A924 to be beneficial to manufacturers, purchasers, inspectors, and quality-control personnel.

ASTM A924 Testing Process and Data Collection

The technician selects representative samples and prepares specimens according to the requirements of the applicable product specification. The technician records material identification, heat or lot information where applicable, sheet dimensions, coating designation, specimen information, test conditions, and measured values. The analyst takes measurements and makes comparisons with the relevant ASTM product specification. The analyst records chemical composition, mechanical properties, coating data, dimensional measurements, surface observations, and any other required data.

Common Challenges and Troubleshooting

One common challenge is applying ASTM A924 without identifying the applicable product specification. ASTM A924 provides general requirements, while the individual product specification establishes important grade, coating, and performance requirements. Technicians should identify both documents before beginning the evaluation. Inconsistent coating measurements can result from nonuniform coating distribution, surface condition, specimen location, or improper measurement technique. Technicians should follow the applicable coating measurement procedure and select representative sampling locations.

• Chemical composition results are reported according to the applicable steel specification, commonly using mass percent (%) for individual elements. Mechanical properties may include yield strength, tensile strength, and elongation, with strength values commonly reported in MPa and elongation in %. Coating measurements may be reported using the units specified by the applicable product specification.
• The technician records material identification, heat or lot information, steel grade, coating designation, specimen dimensions in mm, coating measurements, mechanical-test conditions, and dimensional measurements. The analyst documents measured chemical composition, mechanical properties, coating characteristics, dimensional results, surface observations, and applicable calculations.
• The report contains the steel identification, product specification, grade, coating type and designation, specimen information, dimensions, chemical results, mechanical properties, coating results, surface observations, test conditions, and applicable acceptance requirements.
• Because ASTM A924 is a general specification, the specific acceptance limits and required test results depend on the individual ASTM product specification being applied. Analysts should therefore interpret results against the complete set of requirements applicable to the ordered steel product.
• Consistent sampling, specimen preparation, dimensional measurement, coating evaluation, mechanical testing, equipment calibration, surface inspection, and documentation allow technicians and analysts to provide reliable and comparable ASTM A924 results.

Link to ASTM A924