|
Currently the ship and component materials corrosion resistance is evaluated using real sea coupon test method, this method has the real conditions, the test is simple and the results more reliable advantages, but there are also some disadvantages, such as long test cycle, usually the shortest test period of one year beyond the control of environmental factors, poor reproducibility of test results, test failure caused by the loss of the specimen at higher risk. These drawbacks restrict the new materials and new technology rapid application in practice. In this paper, in seawater added H2O2, enhanced cathodic depolarization to simulate and accelerate the hull steel seawater immersion zone corrosion. Using the weight loss method, corrosion morphology observation, analysis and electrochemical corrosion products from the test simulation, acceleration and reproducibility was evaluated three accelerated testing laboratory simulation of natural seawater exposure test the correlation, using rotating disk disk electrode technique of simulated acceleration mechanism and the main factors, the establishment of seawater immersion corrosion indoor simulation accelerated test methods. Main work and conclusions are as follows. 921A hull steel was studied in seawater, seawater 0.01mol / L H2O2 solution, water and seawater 0.01mol/LKClO4 0.01mol/LNa2S2O8 solution corrosion behavior of the solution. The results show that, 921A in seawater, seawater 0.01mol / L H2O2, seawater 0.01mol / L Na2S2O8 and seawater 0.01mol / L KClO4 solution polarization curve similar Na2S2O8, H2O2 and 921A KClO4 have accelerated corrosion in seawater, the speedup was 15,2.8 and 2.5. 921A in seawater 0.01mo1 / L H2O2 solution was ulcer-like uniform corrosion, corrosion product is α-Fe2O3, γ-FeOOH and Fe3O4, and in seawater corrosion similar to that in seawater 0.01mol / L Na2S2O8 solution corrosion morphology, products and in seawater varies greatly. KClO4 make the solution acidic. Therefore, H2O2 is most suitable for accelerating the hull steel corrosion in seawater depolarizing agents, seawater addition of H2O2 to simulate accelerated hull steel in seawater immersion zone corrosion. Studied the hull steel 945,921 A, 907A, E36 and Q235 natural exposure in seawater accelerated testing experiment and simulation of corrosion was investigated indoor simulation simulate accelerated test method, acceleration and reproducibility. The results show that the steel hull marine natural exposure simulation experiment and after the acceleration test, the corrosion morphology, surface corrosion products of the same composition and structure, the corrosion rate is reduced as the immersion time. The steel hull of natural exposure test in seawater and seawater 0.05mol / L H2O2 in the corrosion resistance of the same order. Hull steel 921A, E36 and Q235 soaked in sea water, sea water 0.01mol / L H2O2 and seawater 0.05mol / L H2O2 solution within 24h negative shift of the corrosion potential of about 0.15V, subsequent changes in volatility in the stable after 400h at -0.63 between-0.68V. Hull steel 921A, E36 and Q235 in the sea, the sea 0.01mol / L H2O2 and seawater 0.05mol / L H2O2 immersion of two weeks, the polarization resistance decreases and then increases. As the immersion time, the surface coverage of the corrosion products blocking the diffusion of oxygen, polarization resistance increases, reducing the corrosion rate of metals; two weeks after the formation of relatively stable sample surface rust, polarization resistance tends stabilization; for 7 weeks, a large accumulation of metal surface corrosion products, pseudo-capacitance occurred, the determination of the polarization resistance is not accurate. Analysis of the hull steel 921A in natural seawater exposure test and indoor simulation acceleration test corrosion mechanism. The results showed that, 921A in seawater in H202, H202 surface 921A only increased cathodic reaction intermediates, and promote the reduction rate of the cathodic surface 921A, 921A of the etching rate increases, but no change in the corrosion mechanism. Studied the effects of accelerated testing simulation speedup of the main factors. The results show that the addition of H2O2 and stirring for a period of time in the simulation 921A acceleration of the test solution have a major impact. When water is added 0.8mol / L H2O2, solution temperature of 70 ℃, the right solution is continuously filled the air and changed weekly test solution test methods can be used as water immersion simulation Indoors under accelerated test methods.
|