Brian Dalder Forum Moderator 180 Posts
Re: Corrosive liquid and materials24 September 2007 at 1:29pmUnless they are very dilute, water solutions of chlorine make strong oxidizing acids due to dissolution according to the following reaction:
Cl2 + H2O ---> HCl + HOCl
This is what occurs in the chlorination of potable water. However, the corrosivity is low since the residual chlorine levels are also low (typically less than 1 ppm). You do not say what chlorine concentration you will be running. If it is low (ppm levels) then many materials of construction will work. However, the corrosivity increases rapidly with increased chlorine concentration. For example, the corrosion rate of carbon steel is 12 mpy (mils per year) at 83 ppm but 150 mpy at 393 ppm. Water saturated with chlorine is corrosive to all common metallic materials of construction. Chlorine water attacks most metals and alloys by general corrosion or by localized pitting and crevice corrosion of stainless steels. For room temperature solutions, the most cost effective materials are the non-metals like polyethylene or polypropylene. The least expensive metals that can be used for chlorine water are the Ni-Cr-Mo alloys like alloy 625 or alloy C-276. With the possible exception of some high silicon irons, the materials you asked about (stainless steel, cast iron, and bronze) would not generally be recommended for saturated chlorine water.
Are there chemical plants that utilize and circulate solutions of chlorine, and if so, what are the preferred materials used for piping and pumping components? Is stainless steel, bronze or cast iron preferred for these chlorine solution processes?
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