Exploration On A New Chromium Free Coloring Process For Stainless Steel

Colored stainless steel has not only decoration effect but also the excellent features of the common stainless steel,Such as outstanding corrosion and wear resistance.Traditional coloring technology for stainless steel(inco method)involved using of hexavalent chromium ion,leading to serious environmental pollution and also bring harm to the health of operating person.In the inco methode,the coloring temperature is high and energy consumption is huge,so the cost of the equiment is high.As the people's consciousness of environmental protection enhancement,the traditional stainless steel coloring technology could no meet the development needs of society,so seeking for chromium free or low chromium coloring process has become an increasingly popular research topic.In this paper,a new coloring process by using ammonium molybdate as main reagent was deveolped and the optimal coloring reaction parameters were explored.The specific works are as following.1.the elements of vanadium(V),molybdenum(Mo),manganese(Mn)which have similar chemical properties of chromium(Cr)were choosed as the targets.The coloring performance of the vanadate(toxic),permanganate,molybdate was comparatively researched.It was found that molybdate based formula is the best among the three in solution stability,coloring performance,and chemical property of the colored stainless steel.2.For the ammonium molybdate based coloring solution,the additives EDTA,boric acid,MnSO4 were used to improve the coloring performance.The orthogonal experiments were used to optimize the process and formula.And the optimal parameters were obtained as ammonium molybdate 100g/L,boric acid 30g/L,EDTA 15g/L,MnSO4 25g/L,temperature of 25?,time of 15min and current density of 10 A/cm2.3.The interference films with golden yellow,burgundy,bottle green,brownness,black colors were successfully produced on stainless steel,by using potential control methode.The composition and suface morphology of films were characterized by energy dispersive x-ray analysis(EDAX)and scanning electron microscope(SEM).Their corrosion resistance and wear resistance were also studied by potentiodynamic polarization and Mechanical friction respectively.And based on the component analysis,the mechanism of membrane forming was analysed.