Study On Preparation And Properties Of Rust Conversion Agent

The removal of rust steel processing is an important part of the coating process. Before painting must put on clean steel rust, otherwise, it will due to rising inflation lead to paint film of rust and corrosion effect is very poor. The traditional derusting technology includes mechanical derusting and chemical derusting, but both of them need machine tools. Besides, many large building Bridges and complex steel structure ship by construction condition component restrictions, it is hard to construct with the mechanical construction method.The rust conversion agent which is made of acrylic emulsion, tannic acid and isopropyl alcohol mixture, could coat on the metal surface to form a layer of physical protection film to prevent the occurrence of chemical or electrochemical reaction. The traditional rust conversion agent typically use toxic substances such as phosphates, phosphate emissions into the environment will produce eutrophication, serious environmental pollution. At present, their use is severely restricted. Anti-rust oil rust resistance is good, but the cost is high, consumption of oil resources, the use of unsafe and difficult, and the post-processing of iron and steel products.In this study, a environmental-friendly rust conversion agent was prepared with the polyacrylic emulsion, tannic acid and isopropyl alcohol which are nuisanceless as the main raw materials, by means of single factor experiment and orthogonal experiment. The neutral salt spray test (NSS), tafel polarization curves, scanning electron microscopy and thermal gravimetric analysis/differential thermal analysis method were used to test its performance. The formular of the rust conversion agent contains (ωt%) 60 %acrylic emulsion,20% pyrogallic acid,10% tannic acid,5% isopropyl alcohol,5% coalescing agent. Execution conditions were obtained by NSS, which showed that rust conversion were applicatieve when the thickness of rust layer was below 60μm, response time was 60min, film-forming temperature was 80℃. NSS resistance was 4 period, humidity resistance time was 8h, immerse resistance in 5%NaCl was 24h.Tafel polarization curve showed that the corrosion current density of rust converted film was reduce remarkable from 2.248×10-2mA/cm-2 to 3.567×10-4mA/cm-2, corrosion potential was moving to upright notable from -0.682V upto -0.593V, the rate of corrosion was from 4.697×10-2g·m-2·h-1 fall to7.452×10-2g·m-2·h-1. EIS suggested that, the radius of capacitive teactance arc of the rust converted agent wan increased obviously, the real part of impedance Z’rised markablely from 12.47ohm/cm2 to 32.14ohm/cm2, imaginary part -Z" reduced strikingly from -2.68 ohm/cm to-5.23 ohm/cm. In brief, the rust conversion agent had advantages such as convenient construction, low cost, high performance, it would be wide used in the future.