304 Stainless Steel High Temperature Oxidation Coloring Research

Due to the elegant appearance and good mechanical performance,colored stainless steel become popular in decoration industry. With the rapid development of colored stainless steel market, the demand to the colour and style is much bigger. However,most of the current colouring technology still contain Chromium which is harmful to human beings and the environment. Therefore it’s necessary to study a more environmental and safety stainless steel colouring technology. Stainless steel colored by high temperature oxidation method is a green technology and no Chromium pollution during the coloring processes, but the study on the coloring processes and colouration mechanism is still not clear up to now,it has great significance and important referential value to the developing of the coloring technology of stainless steel. In this paper,we studied the effect of high temperature oxidation on the stainless steel color,analyzed the organization structure and composition of the films, the colouration mechanism of stainless steel is also discussed,and improved the ability of corrosion resistance by post-treatment.This paper colouring the SUS304 stainless steel by a high temperature oxidation method,and studied the effect of oxidation temperature and oxidation coloring time effect on the color. It was found that in the coloring temperature 300-700 ℃temperature range the main color is yellow,while the the coloring temperature above800℃,the color become blue and violet.The color on the surface of the stainless steel depends mainly on oxidation temperature, and it’s not necessary to extent oxidation coloring time. In addition, the reflection surface gloss in mirror decreased significantly as the oxidation coloring time increased when clouring in high temperature oxidation interval.XRD test results show that Fe2O3 exists in the film,XPS data showed that Fe exists with Fe2O3,Ni exists with Ni2O3 and Cr exists with Cr2O3,CrO3,CrOOH. The colouration mechanism of high temperature oxidation method is similar to chemicalcolouring process,the color is mainly caused by the interference of light. As the coloring temperature increased,the grain become more and more and the grain size gradually increase,the curve of oxidation kinetics follows the logarithm law at 500℃and the quadratic curve law at 800℃. The oxide films surface colored in 500℃ is more flat,whilethe oxide films surface colored in 800℃ is rough and spinelstructure exist in the oxide films, which caused the low mirrorluster degrees and good hydrophilic.The corrosion resistance of stainless steel after coloring decreases sharply. The post-treatment can effectively improve the corrosion resistance of stainless steel after colouring,after 96 hours salt spray test found that the sodium silicate solution is ineffective for edge area and mercaptan solution can achieve a full range of sealing effect, the mercaptan solutionsealing treatment is the best the post-treatment.The hydrophilic of stainless steel surface after post-treatment depend mainly on the hydrophilic of sealing material.