Posted on 2015-05-14 First, the appearance:
In natural light refraction, with the naked eye observation. The basic tone zinc chromate coating should silver gray, can also be obtained by modification of other colors, such as black. Zinc chromate coating should be continuous, seamless coating, bubbles, peeling, cracking, pitting, inclusions and other defects. Coating should be substantially uniform, no obvious local phenomenon too thick. The coating should not discolor, but allows a small yellow spots exist.
Second, the coating amount and the coating thickness of the test:
Standard coating amount of the coating thickness or the coating of different grades divided into four grades, two methods may be used to detect:
1, dissolution weighing method: sample weight is greater than 50g, employs a precision of 1mg balance that was the original mass W1 (mg), the sample was placed in 70 ℃ ~ 80 ℃ of 20% NaOH aqueous solution, soaking 10min, zinc chromium coating has completely dissolved. Sample was taken out, thoroughly washed with water immediately after drying, the coating was dissolved, said mass of test sample after W2 (mg). And calculate the amount of surface area of ??the workpiece S (dm2), according to the following formula to calculate the coating amount of the coating of W (mg / dm2):
W = (W1-W2) / S
2, microscope method: press GB / T6462 requirements, using optical microscopy was used to detect the coating thickness.
Third, the adhesion strength test:
Using tape test method, the adhesion strength detect zinc chromate coating and the substrate, and the tape test according to GB / T5270-1985 requirements in section 1.4. After the test requirements can not be peeled off the coating from the substrate, or open at the end, but allowing the adhesive tape discoloration and zinc, aluminum grains.
Water resistance test: The specimen was immersed in deionized water 40 ℃ ± 1 ℃, the continuous immersion 240h, after the sample was taken out and dried at room temperature, then the adhesion strength testing, the test results should meet the requirements of adhesion strength test. Adhesion strength test should be carried out within 2h specimen was removed from the post of deionized water. After the water resistance test, the coating can not flake or open at the end from the substrate.
Post time: Jan-13-2022