A brief analysis of the performance test method of ship coating re-painting

0 Overview
In the past 20 years, China's ship coating testing technology has achieved rapid development, reached a certain level, developed a series of paint testing standards, improve the standard system. At the same time, the application of testing standards has greatly improved the level of coating testing technology and coating quality, shortening the gap with the industrial developed countries of coating testing technology. Since the late 1980s, China's ship heavy anti-corrosion coatings have entered a golden period of rapid growth, becoming one of the fastest growing coatings industry, the earliest in line with international standards, accounting for the largest market share of industrial coatings . It is expected that in the next 5 to 10 years, China's ship heavy anti-corrosion coatings and coatings will still show a rapid development trend.
the promotion and application of long-lasting heavy anti-corrosion coating system, so that anti-rust performance often reaches 10 years or more effect, so different service life of primers and finishes in the chemical curing type paint repair process caused heavy coating problems, usually chemical curing Coatings in the coating of the longest coating interval time limit, subsequent coating needs to be polished treatment, not only time-consuming, reduce the effectiveness of coating, but also cause environmental pollution, and its effect is often not satisfactory, far from the chemical combination between coatings. In order to overcome the problem of heavy coating of the longest coating interval of the coating, the re-coating of the coating came into being.
repaintable coating is a new generation of paint, its re-painting performance detection methods, especially for the hull paint re-painting testing at home and abroad has not yet formed a unified standard, therefore, seriously restrict the development and application of China's new generation of coatings. Combined with his own work experience and reference to relevant information, the author recommends several shell paints with practical value and several important parts of the cabin coating re-painting performance test methods, in order to speed up the development and application of repaintable coatings, in order to promote the progress of coating detection technology.
1 Test Part
1.1 Hull Paint Recolor Performance Test Method
1.1.1 Test Principle
(1) Thermal Acceleration Curing
Thermal Acceleration Curing Resailability Test Principle simulates a recoating test after a coating has been completely cured over a long period of time.
(2) Atmospheric exposure (GB/T 9276-1996)
The principle of atmospheric exposure re-coating testing is to assess the re-painting test after exposure of coatings in outdoor natural environments.
(3) Ultraviolet Aging (GB/T 14522-1993)
The principle of UV aging recoated testing is to simulate the recoated testing of coatings by outdoor solar UV rays.
1.1.2 Sample preparation
the test plate required to prepare the sample should comply with the GB/T 912-1989 ordinary carbon steel technical requirements, specifications determined by the test performance test requirements, its surface treatment in accordance with GB/T 9271-1988 regulations.
(1) Heat-accelerated curing sample preparation
the re-coatable paint directly applied to the test plate, placed 24 h at room temperature conditions, the dry sample after (80±2) degrees C, 200 h treatment, and then applied a re-coatable paint on the sample surface, at room temperature after curing 7 d re-applying.
(2) Atmospheric exposure sample preparation
according to the re-coatable hull paint matching system coating test board, test sample in the indoor maintenance 7 d, and then carried out Xiamen ocean atmosphere exposure test for 6 months, 12 months. Wipe off the surface dust of the sample paint film after exposure with a dry cloth, and then apply 1 re-coatable hull finish on the sample surface, cure 7 d at room temperature and then re-apply the adhesion test.
(3) UV aging sample preparation
according to the repaintable hull paint supporting system coating test board, sample in-room maintenance 7 d, according to GB/T 14522-1993, respectively, 200 h, 500 h, 1,000 h UV aging test. After the test sample surface coating 1 can be re-coated paint, at room temperature curing 7 d after re-applying adhesion test.
1.1.3 Performance
repassing performance tests were performed on samples by ASTM D 4541 and GB/T 9286-1998, respectively. Using Xiamen Shuangrui Ship Coatings Co., Ltd.'s 725-BS43-91 re-coatable polyurethane paint, a series of re-coating tests were carried out according to the coating re-painting performance test method.
samples are prepared according to the following supporting system:
primer: 725-H06-21 epoxy zinc-rich primer, (40±10) sm.
paint: 725-H53-81 epoxy cloud iron anti-rust paint, (100±10) sm.
: 725-BS43-91 Polyurethane finish, (120±10) sm.
re-coated adhesion, the test results are seen in Table 1, Table 2, and Table 3, respectively.
Ship Coatings Inspection
1.2 Ship Liquid Cabin Coating Recoated Test Method
1.2.1 Test Principle
Ship Liquid Cabin Coating Recoated Test Method simulates the environment during the actual long-term application process, and detects the indoor acceleration test method of coating recoated performance during continuous cleaning of the cabin and its maintenance.
1.2.2 Sample preparation
the test plate required for the test sample is hot-rolled low-carbon steel, blasting treatment reached Sa 2.5 level or above, test plate specifications by the test performance test requirements, sample preparation according to GB /T 1727-1992.
1.2.3 Test Method
(1) Heavy coating test procedure for fuel/seawater ballast coatings:
(a) At (27±6) degrees C, samples are soaked in natural seawater or 168 h of artificial seawater as prescribed by GB/T7790-1996;
(b) at (27±) At a temperature of 6 degrees C, the sample is soaked in 168 h with the fuel specified in the ASTM D 1655 standard, and the interval between
the two steps is not more than 8 h;
(2) Special seawater ballast coating re-coating test procedure:
(a) At (27±6) degrees C, the sample is sampled with natural seawater or GB/T7790-1996 Man-made seawater soaked 120 h;
(b) naturally dried 48 h;
(c) At 80 degrees C, the sample was soaked in natural seawater or 2 h in man-made sea water as prescribed by GB/T 7790-1996.
(3) Water tank coating re-coated test procedure:
(a) At (27±6) degrees C, the sample is fully immersed in distilled water as specified by ASTM D1193 120 h;
(b) naturally dried 2 d;
(c) at 80 degrees C, the sample is soaked in distilled water 2 h.
(a) to (c) for 1 complete cycle, repeat 25 cycles, and record the status of the coating after each cycle. After 20 cycles, wash the sample with tap water, dry 48 h, and then re-apply 1 test coating in the upper 1/3 area of the sample, apply a matching finish (or a matching system of coated primer and finish) to the lower 2/3 area of the sample, sealing the edge. Dry at standard room temperature for 1 week and then complete the last 5 cycle tests. After 25 cycles are completed, the coating system is re-coated: the re-coating strength must not be less than 50% of the original coating (ASTM D 4541).
2 Results and discussion
(1) Remaintable polyurethane hull coating re-painting test results show that the damage site is mostly heavy paint film damage, indicating that the site is the paint re-painting problem should be of particular concern. The test also shows that: after heat-accelerated curing, 6 months, 12 months of atmospheric exposure, 200 h, 500 h, 1 000 h UV aging, the coating film attachment strength has not been significantly reduced, but also with the actual application of the coating over the years, the re-coating test method proposed in this paper is credible.
(2) Ship liquid cabin coating re-coating test, whether is ISO standard or ASTM, MIL-PRF-23236C standard, are more mature methods, and are evaluated at no less than 50% of the original attachment strength. The author believes that the cabin coating is best combined with the most demanding conditions in the actual use process to simulate aging, so that the indoor acceleration test results can be consistent with the expected effect of the actual use process.
(3) With the continuous progress of science and technology and detection methods, testing methods are constantly improving. The re-coating test method is a new test method with the progress of coating technology. Using the test method combining natural state and indoor acceleration state can not only observe the difference between the two, but also verify the compound coating performance of the coating at the same time, which is of some reference significance to the domestic detection recoating.