Abstract
To prevent corrosion by MIC (Microbiologically Influenced Corrosion) of the heat exchanger's carbon steel tubes in Mitsui Chemicals Osaka Works (MCI Osaka), we improved the cooling water recirculating system. Furthermore we have studied the ability of several kinds of inhibitors used in our water cooling system.
To reduce MIC potential, we have changed the sterilizing method from the intermittent addition of bactericide (NaClO) to the continuous addition. As a result, life of the heat exchangers were prolonged more than two times. Additionally, we have studied the ion selective property of synthetic iron rust membranes (β-FeOOH) adsorbed the inhibitor, such as OP (Ortho Phosphoric acid), PBTC (2-Phosphno Butane-1, 2, 4-TriCarboxylic acid), HEDP (Hydorxy Ethilidene-1, 1-Di Phosphonic acid), PAA (Poly Acrylic Acid) and so on.
Cation selectivity was increased in the order: OP<PAA<HEDP<PBTC. From this fact, it was found that HEDP and PBTC is more effective for corrosion prevention compared to PAA and OP. Iron rust adsorbed the inhibitors containing HEDP or PBTC has ability of preventing corrosive anion like chloride ion from penetrating it into metal surface.
