The “Toyota TSH 1509G Chemical Resistance of Paint Film” standard developed by Toyota Vehicle Company describes test methods to control the effects of chemicals such as acid and alkali on the paint film.
The spot method described in this standard includes procedures for water discoloration resistance, alkali discoloration resistance, and acid discoloration resistance.
According to the water discoloration resistance procedure, a polyethylene ring with an inner diameter of 38 mm and a height of 15 mm is placed on the test panel prepared by the specified method, and is pressed tightly against the test panel with a rubber band or other suitable pressing device. 5 mL of distilled water is dripped into the opening. The opening is closed using a glass or polyethylene or stainless steel plate and kept in a thermostatic container maintained at 55 degrees plus/minus 1 degree for 4 hours. After the test, the pressing device is removed, the test panel is washed with water and wiped. The conditions of the coated surface (discoloration, gloss, shrinkage, cracking, swelling and peeling) on the tested part are observed. The ring mark is not included in the evaluation. The mirror gloss is measured as specified in the Toyota TSH 1519G standard. Color measurement is carried out according to the Toyota TSH 1518G standard, and the color difference between the tested and untested areas of the coating is calculated. A plate that can seal the cylinder as tightly as possible is used to minimize the evaporation of the test solution.
According to the alkaline discoloration resistance procedure, a polyethylene ring with an inner diameter of 38 mm and a height of 15 mm is placed on the test panel prepared by the specified method and pressed tightly against the test panel with a rubber band or other suitable pressing device. 5 mL of 1/10 N sodium hydroxide water solution is dripped into the opening. The opening is closed using a glass or polyethylene plate and kept in a thermostatic container maintained at 55 degrees plus/minus 1 degree for 4 hours. After the test, the pressing device is removed, the test panel is washed with water and wiped. The conditions of the coated surface (discoloration, gloss, shrinkage, cracking, swelling and peeling) on the tested part are observed. The ring mark is not included in the evaluation. The mirror gloss is measured as specified in the Toyota TSH 1519G standard. Color measurement is carried out according to the Toyota TSH 1518G standard, and the color difference between the tested and untested areas of the coating is calculated.
According to the acid discoloration resistance procedure, a polyethylene ring with an inner diameter of 38 mm and a height of 15 mm is placed on the test panel prepared by the specified method, and is pressed tightly against the test panel with a rubber band or other suitable pressing device. 5 mL of 1/10 N sulfuric acid water solution is dripped into the opening. The opening is covered with a glass or polyethylene or stainless steel plate and left at 20 degrees plus/minus 2 degrees for 24 hours. After the test, the pressing device is removed, the test panel is washed with water and wiped. The conditions of the coated surface (discoloration, gloss, shrinkage, cracking, swelling and peeling) on the tested part are observed. The ring mark is not included in the evaluation. The mirror gloss is measured as specified in the Toyota TSH 1519G standard. Color measurement is carried out according to the Toyota TSH 1518G standard, and the color difference between the tested and untested areas of the coating is calculated.
The immersion method described in this standard includes alkali resistance and acid resistance procedures.
According to the alkali resistance procedure, the test panel is prepared using the specified method. The edges and back of the panel, if these parts are uncoated and the panel is metal, are covered with a suitable material before starting the test. A 1/10 N sodium hydroxide solution is poured into a 500 mL beaker and kept at 20 degrees plus/minus 2 degrees. The sample is immersed in the solution for the specified time, then rinsed with clean running water. It is placed upright indoors and left for 1 hour. Then, the coated surface is observed for any gloss, discoloration, cracking, blistering, peeling, holes, softening, etc. The portion of the sample approximately 6 mm from the edge is not subject to evaluation.
According to the acid resistance procedure, the test panel is prepared by the specified method. The edges and back surface of the panel are covered with a suitable material before starting the test if these parts are not coated and the panel is metal. 500/1 N sulfuric acid water solution is poured into a 10 mL beaker and kept at 20 degrees plus/minus 2 degrees. The sample is immersed in the solution for the specified time, then washed with clean running water. It is left indoors overnight. Then, it is observed whether there is gloss, discoloration, cracking, swelling, peeling, holes, softening, etc. on the coated surface. The part of the sample approximately 6 mm from the edge is not subject to evaluation.
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