company news about What are the Common Abrasion Tests Used Internationally?

What are the Common Abrasion Tests Used Internationally?

In today's society, the widely used testing instruments for wear resistance include the wear test machine, scratch tester, oscillation test machine, and linear wear tester. The formulation of the standard for coating wear resistance test methods has unified and standardized the detection methods and quality requirements for different materials, and also provided the necessary design basis for the development and research of various types of wear resistance test instruments. Next, Lonroy will introduce several commonly used wear tests for you.

Rotary friction rubber wheel method (Taber test)

The methods and instruments specified in the national standard GB/T1768--79 (89) have the same working principle, but they do not stipulate the rotational speed of the rotating disc. Moreover, the test results are only expressed by a single method, namely the quality loss (weight loss method) of the coating after being ground at the specified grinding speed. The rotating friction rubber wheel method can be widely used for the wear resistance tests of coatings, platings, and metals and non-metallic materials. However, the rubber grinding wheels used for grinding need to be frequently adjusted and updated in time. The international standard ISO7784.2--97 stipulates the use of the rotating friction rubber wheel method to determine the wear resistance of coatings, that is, under the specified test conditions of a rotational disc speed of 60 r/min and a certain load borne by the pressure arm, a hard rubber friction wheel with diamond abrasive embedded is used to wear the surface of the coating. The wear resistance can be expressed and evaluated by two methods: the average value of the coating quality loss (weight loss method) after the specified grinding speed is used for grinding or the average grinding speed (revolutions per minute method) required to wear a certain thickness of the coating. Compared with the two methods, the weight loss method has strict requirements for the weighing accuracy of the sample, but it is not affected by the thickness of the coating; while the revolutions per minute method is intuitive and convenient, and does not require weighing, but the measurement of the grinding thickness of the coating is very strict.

Test method for coating wear resistance

The coating wear resistance refers to the ability of the coating surface to resist certain mechanical actions. It is usually measured through tests such as grinding with a grinding wheel or sand particle impact. It is one of the important characteristics of coatings that are frequently subjected to mechanical wear during use, and it is closely related to other physical properties such as hardness, adhesion, and flexibility of the coating. The commonly used coating wear resistance test methods and their main technical features in both domestic and international fields.

Sand washing and scouring test method

By using this testing method, the selection of natural abrasive materials will have a direct impact on the test results. Therefore, strict requirements are imposed on the hardness, particle size and geometric shape of the abrasive particles. The national standard GB/T5237.5—2000 stipulates that standard sand that meets the requirements of GB/T178—77 standard should be used as the abrasive material. The ASTM D968—93 standard stipulates that the wear resistance of organic coatings should be determined by the drop sand wear test apparatus, that is, natural quartz sand from the specified origin should be used as the abrasive material. Through the test apparatus' conduit, it is dropped freely from a certain height to wash the surface of the sample, and the volume (L) of the abrasive material consumed to wear a certain area of the unit thickness of the coating is measured. The wear coefficient is calculated to evaluate the wear resistance of the coating. It should be noted that in the above two standards that adopt the drop sand flushing test method, although the wear test apparatus with the same main technical parameters are used, due to the different particle sizes of the natural sand abrasives used, the flow velocity of the same 2L abrasive material is not the same. Both are specified as 21 to 23.5 seconds, while the latter is specified as 16 to 18 seconds.

Sandblasting impact test method

ASTMD658-81(86) stipulates that the wear resistance of organic coatings is determined by the blast erosion (sandblasting) test. This method is achieved by adjusting the output pressure of the air pump to make the air flow rate at the nozzle of the test apparatus 0.07 m³/min, so as to ensure that an average of (44 ± 1) g of diamond sand is sprayed onto the coating per minute. The wear resistance of the coating is evaluated by calculating the mass (g) of abrasive consumed by the worn area of the unit thickness of the coating. Therefore, the abrasive with a particle size range of 75-90 μm, as specified in the standard, must be selected. The output pressure of the air source and the uniform spray speed of the abrasive become the determining factors affecting the test results.

Revolving wear test method

After a certain number of grinding processes, the wear resistance of the coating is evaluated by the reduction in coating thickness (in μm) or coating mass (in mg), and through the calculation of its wear resistance coefficient. Both ISO8251-87 and JISH8682 stipulate the use of an abrasion wheel wear testing machine to determine the wear resistance of aluminum and aluminum alloy anodic oxide films. This testing method involves making the coated layer and the abrasive paper glued to the outer edge of the abrasion wheel perform a reciprocating motion in a plane. After each pair of strokes, the abrasion wheel rotates by a small angle (0.9°). Because the test conditions of this method are easy to control and do not have problems such as wheel adjustment, aging, sand flow rate, and sand beam shape that are difficult to control in other methods, the test results have good repeatability. Moreover, in addition to the coated layer, this method has been widely used for wear resistance tests of plastics, rubber, and metal materials.

Our country has already established the national standard GB/T1768—79 (89) "Method for Measuring the Wear Resistance of Paint Coatings". In recent years, it has been stipulated in GB/T5237.5—2000 to use the drop-sand wear testing machine to measure the wear resistance of fluorocarbon paint coatings on the surface of aluminum alloy building profiles. In summary, it is not difficult to see that currently, there are various methods for testing the wear resistance of coatings and coatings layers at home and abroad, each with its own characteristics. Although people's understanding of the evaluation of various test methods and their application performance is not entirely the same, when it comes to the development and promotion of multiple detection methods, the rotation friction rubber wheel method, the drop-sand method and the sandblasting method are still more commonly used.

To date, industrialized countries have corresponding wear test methods for various materials. For instance, the Japanese Industrial Standard JISH8503 specifies the test method for the wear resistance of metal coatings; JISH8615 describes the wear test of chromium electroplated coatings; for example, the American Society for Testing and Materials standards ASTMD968-93 and ASTMD658-81 (86) respectively stipulate the use of the drop-sand method and the sandblasting method to determine the wear resistance of organic coatings; in the international standard SO7784.2-97, the rotational friction rubber wheel method is adopted to determine the wear resistance of color paints and varnishes; in IS08251-87 and JISH8682, the friction wheel abrasion test machine is used to determine the wear coefficient of the anodic oxide films on aluminum and aluminum alloys surfaces.