Study Of Derusting Coating And Its Application On The Thermal Spraying

Non-sand-blasting thermal spraying anti-rust coating is directly painted with anti-rust primer on rust substrate material, and then painted with some granular padding non-sand-blasting particular primer, which can form a rough surface that thermal spray needed. Based on the rough primer, technology of thermal spraying, sealing and then painting with finish coat are followed. The compound coatings can get the goal of long time corrupt protection by shield from environment and cathode protection.Firstly, The descaling agent system of phosphate acid-phytic acid ,which have better conversion capacity and rapid conversion rate, was firstly chosen by contrast it with phosphate acid-tannin in the paper. Phosphate acid and tannin quality with a ratio of 10: 1 was finally determined as one pack of the derusting primer by contrast with the influence of the weight ratio of phosphate acid in different descaling agent on the coating properties. The derusting effect and mechanical properties of the coating achieved the best condition when adding the amount of 60% in the derusting primer.By comparison experiments, epoxy resin E-44 was chosen and modified by phosphate acid to acquire a certain degree of infiltration and rust conversion capacity to rust layer; long oil alkyd, which have a certain toughening effect to prime, was chosen as one kind of filming material. High-sub-amino amino resin as a cross-linked filming resin was also chosen to catalytic reaction in acidity system of containing descaling agent. The quality proportion of filming resin in another pack was finally determined. It is modified epoxy resin (30%), alkyd (20%), amino resin (20%), xylene (15%) and n-butanol (15%). Adopting in the above composition of derusting primer, the properties of anti-rust coating were determined as follows: achieveing better effect of derusting, adhesion is the 1st grade, flexility is less than 1mm, the impact strength surpass 50 kgf·cm, water-resistant is up to 260h, brine resistance is 240h.Then, influence of choice and dosage of each pack in non-sand-blasting primer of three packs on the properties of primer were discussed. Optimization of three highly efficient pollution-free pigments and the best dosage of three pigments were ascertained by the influence of water and brine resistance on non-sand-blasting primer. Lager granularity padding of proper granularity was chosen and surface treated by silane coupling agent KH 560. Influence of granularity and dosage of lager granularity padding was also discussed and finally ascertained the optimum dosage. At the same time, influence of the variety and dosage of epoxy and its curing agent on properties of the coating was discussed, and compound epoxy resin E-20 and E-12 as filming material of non-sand-blasting was chosen and low-molecular-weight polyamide as curing agent was also chosen. Ultimately, the composition of non-sand-blasting thermal spraying was ascertained.Morphology of the internal structure of compound coatings was observed by the photographs of metallographic analysis. The results show that one part of the surface granule of coarse layer was adhered by filming resin in the non-sand-blasting coating, while the other part throw open to the thermal spraying layer, hooked in the internal molten metal of thermal spraying and brought 'cast anchor' effect. Molten metal of thermal spraying penetrate into the interspace of coarse layer and the two layers become a mechanical lock. Thus, locked of each other, the two coating layers were combined closely by the formed connection of anchor-hold and incrustation. At present the compound coating obtains salt spray fog resistance reach 1500h. It estimated that salt spray fog resistance may reach above 3000h.