There are three reasons for the blistering of the paint film. One is that bubbles are formed due to the expansion of the paint film when it absorbs water, and this phenomenon is even worse when the temperature rises and the pigment contains water-soluble salts; Corrosion of the metal base plate, the volume increases and the formation of bubbles. The evaluation method of foaming phenomenon is as follows:
(1) According to the evaluation of the size of the bubble, it is generally divided into four types, the smallest diameter is 1 mm and below 1 mm; the second is 2 mm and 3 mm, and the largest is 5 mm and above 5 mm.
(2) According to the evaluation of the denseness of the bubbles, it can be divided into four grades, such as sparse (expressed by F), medium (expressed by M), dense (expressed by MD) and dense (expressed by D).
(3) According to the evaluation of the distribution area of the bubbles, the standard sample is generally divided into 100 equal parts, and the percentage of the sample taken by the blisters is measured.
