An important step in the quality assurance process is to conduct salt spray testing to verify the corrosion resistance of fasteners such as ISO 4017 M10×120 8.8U TZN screws. These tests assure the durability and reliability of the screws in typically corrosive environments, such as outdoor industrial areas. Here, we’ll cover the key requirements for the salt spray test for this specific screw, identify the applicable ISO standards, and provide detailed insights into its importance.

What is the Purpose of a Salt Spray Test?

A salt spray test is a standardized corrosion test used to evaluate the resistance of coated or uncoated materials to oxidation over time. This test examines how well the wall finish protects the substrate material from corrosion under adverse conditions for fasteners such as ISO 4017 M10×120 8.8U TZN screws.

This test is essential for TZN (trivalent zinc-nickel) coated screws. Testing for the protective effect of these coatings is important because they are designed to provide excellent corrosion resistance.

Key Requirements for the Salt Spray Test for ISO 4017 Screws

1. Sample Preparation

The screws must be cleaned and cleaned before the test. The basic preparation steps include:

• Surface Cleaning: To remove any grease, dirt, or contaminants affecting test results.
• Maintaining coating integrity: Ensure that the screw coating remains intact during operation.

2. Test Procedure

Salt spray testing follows the controlled procedure specified in ISO 9227, the international standard for salt spray (or fog) testing:

1. Placement: To ensure uniform exposure to the salt mist, the screws are angled between 15° and 30° within the salt spray chamber.
2. Solution Composition: The salt spray chamber is filled with a 5% sodium chloride (NaCl) solution with a pH between 6.5 and 7.2.
3. Temperature Control: For complete uniformity throughout tests, the chamber's temperature is kept at 35°C ± 2°C.
4. Exposure Duration: Depending on the precise corrosion resistance class needed, the exposure time for TZN-coated screws, such as ISO 4017 M10×120 8.8U, normally varies between 240 and 480 hours. 

3. Inspection Criteria

After testing, the screws are inspected to:

• Red rust formation: The presence of red rust indicates substrate degradation and coating failure.
• White rust formation: White rust is a sign of premature coating degradation but does not necessarily indicate contact with the substrate.

The pass/fail requirements are based on the requirements specified in the applicable product standard.

Applicable ISO Standards for the Salt Spray Test

Several ISO standards determine the salt spray test procedure and performance requirements of the ISO 4017 M10×120 8.8U TZN screw. These include:

ISO 9227: Salt Spray Testing

This standard describes the procedure for neutral salt spray (NSS) tests. It specifies parameters such as the preparation of the NaCl solution, the configuration of the test chamber, and the duration of incubation.

ISO 4042: Fastener Coatings

ISO 4042 covers specifications for electroplating on fasteners, including requirements for zinc-nickel (TZN) plating. It provides guidance on coating thickness, adhesion, and corrosion resistance parameters.

ISO 898-1: Mechanical Properties of Fasteners

This standard specifies devices in packaging materials made of carbon steel and steel alloys. Grade 8.8 for ISO 4017 screws specifies specific tensile strength and yield stress requirements, which remain unaffected by the salt spray test.

Detailed Insights on the ISO 4017 M10×120 8.8U TZN Screw

The ISO 4017 M10×120 8.8U TZN screw is a hexagon head screw made of medium-carbon steel. His nickname provides important information:

• M10: Nominal diameter of impact 10 mm.
• 120: The length of the screws is 120 mm.
• 8.8U: This means that it is a high-strength fastener with a tensile strength of 800 MPa and a yield strength of 640 MPa.
• TZN Coating: A trivalent zinc-nickel electrode coating that provides superior corrosion resistance compared to standard zinc coatings.

These screws are frequently utilized in industrial and automotive sectors where corrosion resistance and mechanical strength are crucial.

Factors Affecting Salt Spray Test Results

Although the salt spray test is a commonly used technique to assess corrosion resistance, several factors affect its results, such as:

• Coating Thickness: Although thicker coatings typically provide higher protection, they may also necessitate longer test exposure times.
• Surface Pre-Treatment: Consistent outcomes are made certain by thorough surface cleaning.
• Environmental Conditions: To maintain consistent conditions over the test duration, salt spray test chamber calibration is essential.

Interpreting the Salt Spray Test Results

Salt spray test results are usually presented hours before visible corrosion occurs:

• 240 Hours: Demonstrate basic resistance suitable for moderate environmental conditions.
• 480 Hours: High corrosion resistance to aggressive environmental conditions.

Screws such as ISO 4017 M10×120 8.8U TZN typically require at least 480 hours without red fading to meet stringent technical standards.

Applications of Salt Spray Testing for ISO 4017 Screws

Where screws are regularly exposed to moisture, chemical, or temperature changes, salt spray testing is necessary. The most important controls are:

• Automotive Industry: Used in vehicle suspensions, undercarriage fasteners, and engine parts.
• Construction: Required for construction support and exterior installations.
• Marine Applications: Essential for screws utilized in offshore or coastal atmospheres. 

Conclusion

ISO 4017 M10×120 8.8U TZN screws are made to endure severe weather conditions, and salt spray testing is crucial to ensuring their dependability and longevity. Industries that manufacture products must ensure that their supply chain satisfies the highest standards by adhering to relevant standards, such as ISO 9227 and other relevant standards. In addition to ensuring functionality, this stringent testing procedure boosts trust in the product’s durability across a range of uses.