[literature express] calcium phosphate can replace zinc phosphate in the preparation of waterborne epoxy anticorrosive coating, and the amount of it is greatly reduced

Key words: anticorrosive coating background: in waterborne epoxy anticorrosive coating, the contribution of pigments and fillers to anticorrosive and antirust performance is next to that of film-forming substances The pigments and fillers of waterborne epoxy anticorrosive and antirust coating should be those with good covering power, chemical inertness, neutral or alkaline, low oil absorption and good chemical resistance For example, iron oxide red is an inert pigment with high chemical stability, which can play a good shielding role as a physical antirust pigment; zinc phosphate is an important antirust pigment, whose antirust mechanism lies in the formation of a solid adhesion complex on the metal surface, and the complexation with the hydroxyl and carboxyl groups in the antirust paint, so that the chemical combination between the film and the substrate can be formed to improve the coating Adhesion and impermeability Sol n Roselli of the National University of La Plata studied and prepared a new zinc free and low phosphate waterborne epoxy anticorrosive coating Calcium phosphate and lanthanum molybdate were added as anticorrosive and antirust fillers, and the anticorrosive properties of the coating were characterized His achievements were published in progress in organic coatings in 2017 Research content: the author has prepared 8 coating formulations as follows: Table 1: the formulation of water-based anticorrosive coating mainly adjusts the addition amount of calcium phosphate and lanthanum molybdate Results and discussion 1 Corrosion potential and appearance characterization after adding fillers Figure 1 corrosion potential of steel with different fillers It can be seen that the corrosion potential of steel can be changed by adding calcium phosphate and lanthanum molybdate The corrosion potential of steel in calcium phosphate suspension is transferred to negative value due to the formation of phosphate layer, while the corrosion potential of steel replaced by lanthanum molybdate is positive The change of corrosion potential of steel in two pigment mixtures has the same trend as that of lanthanum molybdate Fig 2 is an electron micrograph of calcium phosphate and lanthanum molybdate Fig 2 electron micrograph of steel surface (a, adding calcium phosphate, B, adding lanthanum molybdate, C, adding calcium phosphate and lanthanum molybdate) 2 The anti-corrosion effect of the coating the author has carried out the artificial accelerated anti-corrosion test on the seven coatings, the results are as follows: Table 2 salt spray performance test of water-based anti-corrosion coating attempt 3 salt spray photo of water-based anti-corrosion coating It can be seen from table 2 that the salt spray performance of other coatings after 4300h is good except for 3 × coating, and after 5350h, the salt spray performance of 1 × coating, 2 × coating, 5 × coating and 7 × coating is still good The results show that even if the content of calcium phosphate and lanthanum molybdate is low, good results can be achieved, which shows that reducing the content of anti-corrosion pigment can also achieve the ideal anti-corrosion and anti rust effect In terms of coating blistering, it can be seen that the coating began to blister after 2570h, but after comparison, it was found that the coating added with calcium phosphate and lanthanum molybdate had a smaller degree of blistering than that of the coating not added, among which 5 and 7 coatings only blistered after 5350h 3 Constant temperature and humidity test of coating table 3 constant temperature and humidity test of water-based anti-corrosive coating can be seen from table 3 that after 1180, the anti rust effect of 3 × 4 × 5 × 6 × 7 × and 7 × coating is good, but the foaming begins after 216h 4、 Other test authors also proved that calcium phosphate and lanthanum molybdate have good anti-corrosion and anti rust effect by ion impedance test, noise test of paint panel immersed in 0.5M NaCl solution for 39 days, and corrosion potential test of coating The amount of the filler is 1/3 of zinc phosphate Conclusion sol n Roselli et al Add calcium phosphate to replace zinc phosphate in the waterborne epoxy coating to achieve the purpose of corrosion prevention and rust prevention, and add lanthanum molybdate to further improve the effect of corrosion prevention and rust prevention of waterborne epoxy coating It is found that calcium phosphate and lanthanum molybdate are used as anticorrosive pigments instead of zinc phosphate, which not only have excellent anticorrosive and antirust properties, but also reduce the dosage by 2 / 3 The recommended dosage of calcium phosphate shall not be less than 10% of the amount of pigments and fillers Reference materials: Sol n Roselli, Gabriela lendway Gy &; Rik, Gabor m é SZ á ROS, Cecilia dey á, Roberto romanoli Anticorrosive water borne paints free from zinc and with reduced phone content [J] Progress in organic coatings 112 (2017): 27-36 Author: Liu Hangong