PSA D24 1312 Paint Coatings - Chipping Resistance

The standard “PSA D24 1312 Paint coatings - Chipping resistance”, developed by the French automobile company Renault, describes a test method for assessing the chipping resistance of single or multilayer paint coatings applied to a metal or plastic substrate.

The spalling test consists of projecting a defined mass of metal granules at a defined angle of incidence, with a well-defined output and energy, onto a paint coating applied to a test panel. The same test panel is subjected to a second spalling test, identical to the previous one, after being immersed in water at +24 degrees for 40 hours. The resistance to spalling is assessed by the size and density of the flakes after the adhesive tape is applied and, optionally, the number of impacts reaching the substrate.

Major test equipment used in these tests includes:

• The air-conditioned room has a temperature of 23 degrees plus/minus 2 degrees and does not require a hygrometer.
• Metal granule blasting equipment must comply with the PSA VDA 508 standard. This equipment is modified so that the test samples to be chipped are at right angles to the projection axis of the metal granules. The accuracy of the pressure gauge it is equipped with must be plus/minus 0,1 bar.
• The granules are diamond-type quenched cast iron with an angular shape and an average diameter of 3,5 mm to 5 mm, with a Rockwell hardness of 61 to 65.
• FORD tank complies with the PSA D27 1327 standard.
• Sheets are materials of sheet steel, aluminium or plastic with minimum dimensions of 85 mm × 85 mm, as defined in the standards for paints applied to surfaces.
• The adhesive tape complies with those used in the PSA D25 1075 standard.
• The balance is accurate to the gram.
• The stopwatch is used to set the flow time of the metal granules within 10 plus/minus 1 second.
• Deionized water must be available in the laboratory.

Test samples should be representative of the scale to be characterized. In order to ensure this representation, the basic characteristics of the studied population must be revealed. Selection criteria for test samples must be stated in the test report in accordance with the A10 0156 standard. In case of doubt about sampling, the PSA Group should be contacted to learn the directives to be followed.

Steel, aluminum sheets or plastic sheets are used. These sheets receive various paints whose resistance to chipping is to be evaluated. All relevant parameters are recorded for the entire paint range: surface treatment, thickness of each paint layer, curing temperature, etc.

When it is necessary to evaluate the resistance of painted parts to chipping, for example doors, covers, plastic parts, test samples of at least 50 mm × 50 mm are cut from the flattest area of ​​the part, the radius of curvature is at least 1 m, care is taken not to create tension outside the edges of the sample. If the dimensions of this test sample are less than 85 mm × 85 mm, the test sample is bonded to a steel plate with minimum dimensions of 85 mm × 85 mm.

If a relatively flat test specimen cannot be cut from the part (e.g. anti-roll bar, torsion bar, wiper blade, rim, etc.), the part or part of the part is exposed directly in front of the projection window. A cover suitable for the geometry of each part is applied to the back of the part and to the equipment window to prevent granules from escaping outside the equipment. It is also possible to use 2 or more parts placed side by side to cover the window, a more practical method is to avoid using a cover.

Painted test samples are conditioned in storage for a period of at least 16 hours. In the case of paints that can be cured at temperatures below 120 degrees, the 16-hour conditioning is carried out only 7 days after the paint is applied to the test panels.

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 “PSA D24 1312 Paint coatings - Chipping resistance” standard with its trained and expert staff and advanced technological equipment.