CNH MTM0122 Material Test Methods - Chip Resistance of Paint Material Coatings

The “CNH MTM0122 Materials testing methods - Chip resistance of paint coatings” standard, developed by CNH, an American-Italian multinational company, describes a test method for evaluating the chip resistance of paint coatings to gravel impact. This evaluation is applicable to paint film applied to metallic or non-metallic surfaces. This method can also be used to evaluate integrated colored plastic materials. For these materials, the test is designed to determine the effect of gravel impact on the surface appearance.

This test method may involve hazardous materials, devices, and procedures. This test method is not intended to address all safety issues associated with its use or application. It is the user's responsibility to consult appropriate, established safety or health practices and to determine the applicability of regulatory limitations before use.

The testing process is as follows:

• At least two test samples must be subjected to this procedure to evaluate a paint material. For solid colored plastic materials, the adhesion testing procedure for coated surfaces is not required.
• Representative test specimens are selected that have a smooth continuous surface and a test area free of evidence of poor film formation, sagging, solvent pop, pinholes, and the like.
• With the air valve open, the air pressure in the gravel projector is set to 480 plus/minus 20 kPa (70 plus/minus 3 psi).
• Once the air pressure is set, close the valve and fill the gravel chamber with approximately 550 ml of graded gravel (approximately 250 - 300 stones). The graded gravel is collected by scraping the stones through a 9,5 mm sieve, allowing the fines to fall through.
• A test panel that has been cured at room temperature for at least one hour is placed in the panel holding fixture of the gravel apparatus with the coated surface facing the front of the gravel ledge. The gravel chamber lid is closed.
• The air mist is turned on and the gravel is fed automatically or manually for no more than five to ten seconds. The air flow is turned off.
• A sample is removed for evaluation.
• Apply at least 100 mm of tape to the coated surface of the test panel. The tape is pressed firmly, rubbed, and then pulled to remove any loose particles or flakes of paint from the stone-impacted surface.
• The degree of chip resistance is evaluated by the following procedure:
  • A 100 mm x 100 mm square area exposed to stone impacts is selected for evaluation. Transparent film marked with grids is placed over the area to be evaluated. The number of chips in each grid of the 100 mm x 100 mm square is counted and recorded. To determine the chip rating, the total chip count is compared with the values ​​in the table titled "Total chip resistance rating number."
  • The size of a chip is determined as shown in the figure. A transparency can be used to assess chip size. The chip size rating is based on the average of all observed chips and is compared to the values ​​in the table titled "Chip Size Rating."
  • The point of failure is determined using the values ​​in the table titled "Point of Failure." This rating will represent the primary type of failure observed in the evaluated stone impact area.
• Chip resistance to cold exposure:
  • If specified, this procedure may be performed as a cold test with test panels conditioned in a freezer. The test temperature and performance requirements should be specified. Test panels should be held at the specified cold temperature for at least 2 hours.
  • If the test apparatus cannot be operated at the required cold temperature, all setup steps must be completed before transferring the panel from the freezer for testing. Test panels must be maintained at a temperature 5 degrees Celsius plus/minus 1 degree Celsius lower than the specified test temperature to compensate for temperature increases during testing. Testing begins within 10 seconds of removing the test panel from the freezer.

In short, the CNH MTM0122 standard defines a chip resistance test. This standard is part of a series of material/coating durability tests used by CNH to validate protective coatings applied to agricultural, construction, and industrial equipment. The purpose of this standard is to evaluate how well a coating resists fracture when subjected to impact. This is critical for components on equipment such as plows, loaders, and tractors that routinely encounter flying debris.

Although CNH's exact process is proprietary, fracture resistance testing typically includes:

• Preparing coated test panels.
• Hitting with a steel ball or pendulum.
• Measuring the resulting fracture size or flaking of the coating.
• Comparing results with acceptance criteria to ensure durability under real-world conditions.

This standard is considered important for the following reasons:

• Real-world durability: Equipment in agriculture or construction is exposed to stones, gravel, and debris. Chip resistance ensures coatings won't crack or peel under impact.
• Corrosion protection: Coating failures due to chipping expose bare metal, causing rust and shortening the life of the part.
• Quality and branding: High chip resistance reflects the robust build quality that is essential for CNH brands such as Case IH and New Holland.

This standard applies to the following areas:

• Use in research and development and quality improvement studies: Developed for both internal testing and approved external laboratories and manufacturers.
• Industry application: Complies with standards such as “ASTM D5173 Standard guide for on-line monitoring of total organic carbon in water by oxidation and determination of carbon dioxide formed” or “Paints and varnishes - Determination of resistance of coatings to stone impact - Part 1: Multiple impact testing”, but specifically designed for CNH machines.
• Certification: Coatings that pass the CNH MTM0122 standard are approved for use on CNH equipment, ensuring consistent performance across suppliers.

As a result, the CNH MTM0122 standard is a chip resistance test designed to simulate field impacts and ensure coating longevity. It is a critical test among CNH's broader materials evaluation standards. It protects equipment from wear, corrosion, and visual degradation.

Our organization, which has been supporting businesses across all sectors for years through a wide range of testing, measurement, analysis, and evaluation activities, has a strong team of employees who closely follow global developments in science and technology and are constantly improving themselves. In this context, we also provide testing services in accordance with the "CNH MTM0122 Material Test Methods - Chip Resistance of Paint Material Coatings" standard.