How to measure film hardness

Two Methods for Determination of Coating Film Hardness

There are two methods to determine the hardness of the coating film in my country's national standards. The swing rod damping test method (GB/T 1730-93) has been used in the coating industry for a long time, and now the pencil hardness measurement method of the coating film has been added (GB/T 6739-86). The international standard ISO1522 also stipulates the swing rod damping test method.

Whether in GB1730 or ISO1522, the swing rod measurement method of coating hardness specifies two methods, namely Konig and Persoz swing rod damping test and double swing rod damping test. Either of these two methods is based on the same principle; when the swing rod in contact with the coating swings for a certain period, the softer the coating surface, the faster the swing of the swing rod decays, and vice versa.

The method specified in GB6739 is to use pencils of different hardness to scratch the coating film to evaluate the hardness of the coating film, from 6B to 6H, a total of 13 grades. If a 4H pencil can scratch the coating film, but a 3H pencil cannot scratch the coating film, the hardness of the coating film is 3H. This method is generally suitable for measuring harder coatings.

According to the feedback analysis of users of NBCHAO Mall, whether manual or mechanical, as long as the pencil lead is sharpened according to the standard gauge, regardless of the force, if the pencil hardness is not enough, it is impossible to cut it. Therefore, the accuracy of this method is quite good.

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