Volvo STD 423-0009 Adhesion - Paints and Enamels, Knife Technique

The standard “Volvo STD 423-0009 Adhesion – Paints and enamels, blade technique”, developed by the Volvo vehicle company, describes a procedure used to determine the adhesion of a coating to a substrate.

Test panels coated with oven-baked paint systems must be conditioned according to the specified time, temperature, and relative humidity after passing the curing requirements applicable to the paint material in question. Test panels coated with air-drying paint systems must be dried at room temperature (between 18 and 28 degrees Celsius) for 7 days or force-dried at 50 degrees Celsius for 16 hours according to the “ DIN 50014 Standard atmospheres for conditioning and/or testing - Specifications” standard before conditioning is carried out. Test panels coated with two-component paint systems must be dried for 14 days in a normal climate ( at a temperature of 23 degrees Celsius plus/minus 2 degrees Celsius and a relative humidity of 50 percent plus/minus 5 percent ) according to the DIN 50014 standard. If the two-component paint is force-dried, it must be held at 50 degrees Celsius for 48 hours before conditioning is started.

Conditioning must be carried out for at least 50014 hours in a standard atmosphere (23 degrees plus/minus 2 degrees temperature and 50 percent plus/minus 5 percent relative humidity environment) according to the DIN 24 standard.

The main equipment used in these tests includes:

• A sharp knife with a robust design (length of the blade when folded is about 20 cm)
• The test panel should be painted and cured in accordance with the relevant curing window. The adhesion test should be performed on a relevant substrate. For example,
  • 0,8-0,9 mm steel sheet V-1140 STD according to standard 311-0002
  • 0,8-0,9 mm zinc-coated steel sheet V-1159-ZE 120 or V-1159-ZE 120 according to STD 311-0002
  • 1,0-1,5 mm aluminum sheet V-1170 according to STD 311-0002 standard

The panels must be cleaned very carefully, for example with xylene, trichloroethylene, alkaline degreasing or an electrolytic method, and then stored in such a way that there is no risk of corrosion.

When performing tests, the coated surface is scraped with a folding knife in accordance with the shape given in the standard. The contact angle of the knife edge to the coated surface should be approximately 45 degrees. The thumb nail is placed in the scratch and the nail is pressed at a right angle to the scratch to try to remove the paint.

The following grading scale is used in the evaluation:

• 0 = Very good adhesion; paint cannot be removed
• 1 = Good adhesion, paint can be removed only with difficulty
• 2 = Poor adhesion, paint can be removed without effort
• 3 = Very poor adhesion, paint flakes off

The report to be prepared at the end of the tests should include:

• Volvo part number of the test material
• Supplier identification of test material
• Testing according to STD 423-0009
• Adhesion according to degree scale
• Any defects in the substrate such as corrosion etc.

In the paint and coatings industries, paint adhesion testing is often used to determine if paint or coating will properly adhere to the surfaces to which it is applied. Several tests measure the resistance of paints and coatings to surfaces: cross-cut testing, scrape adhesion, tensile testing, and others.

Briefly, the knife crosscut test is a method for determining the resistance of paints and coatings to separation from substrates by penetrating the substrate using a tool to cut a lattice pattern at right angles to the coating. When testing a multi-layer system, this method can be used to determine the resistance of different layers to separation from each other.

Among the numerous tests, measurements, analyses and evaluation studies carried out for businesses in various sectors, our organization also provides testing services defined in the “Volvo STD 423-0009 Adhesion - Paints and enamels, knife technique” standard with its trained and expert staff and advanced technological equipment.