The Study Of Corrosion Behavior And Inhibition Of Metals In Concentrated Alkali Solution

The corrosion of equipment is so serious in alkali industry which including the chlorine alkali industry and the caustic soda industry. Because of the corrosion of equipment, alkali industry has to repair and change large quantity of facility. It seriously influences normal delivery and brings much economic losses and safe incipient fault at the same time. Therefore, studying the corrosion behavior of material and new corrosion inhibitor in concentrated alkaline solution are vital significance and has the practical value.Polarization curve and EIS of five Metals such as Q235, 1Cr18Ni9Ti, pure titanium,titanium alloy and cast iron which are used in basic industry in 40%NaOH Solution was assayed by means of three electrode system. Then using metallographic analysis and SEM rated the micro pattern and corrosion products of corrodible surface. Then study the unity recipe and compound recipe of inhibition of Q235, 1Cr18Ni9Ti and cast iron in concentrated alkali solution initiatively. The important outcomes are introduced as following:1. With the increase of temperature, the degree of corrosion is apparently aggravated. Among the metals, cast iron is the most influencing metal from the temperature and the current density of it is maximal. The titanium alloy and the pure titanium are reverse and the Ep of them is minima.2. The corrosion micro pattern of Q235, pure titanium, cast iron is general corrosion, and the corrosion would be occurred at grain boundary and inclusion previously. The corrosion micro pattern of 1Cr18Ni9Ti and titanium alloy is local corrosion with a lot of micro holes of corrosion on these metals'surface.3. Four kinds of unity recipe of inhibition are inhibitive to Q235, 1Cr18Ni9Ti and cast iron in 40%NaOH solution of 25℃. With the increase of density of unity recipe temperature, the rate of inhibition is apparently aggravated.4. The compound recipe of inhibition is inhibitive to Q235, 1Cr18Ni9Ti and cast iron in 40%NaOH solution of 25℃and 90℃. The rate of inhibition is apparently aggravated with return-service.5. The product would be generated on the matal's surface after use inhibition. And it can separate mediator and metal and reject the corrosion reaction.