INFLUENCE OF SOFT STORAGE RESERVOIR WATER IN INHIBITING EFFECT OF POLYCARBOXYLIC ACIDS

It was the intention of the project to examine the influence of soft s torage reservoir water on the inhibiting effect of polycarboxylic acid s on unalloyed steel, copper and AlMgSi0.5. For the investigations cir cuit equipments consisting of rotating thermostats and in series coupl ed tube test pieces were used. Several inhibitor mixtures were tested in synthetic waters of different composition and in storage reservoir water independence on temperature and flow velocity. At unalloyed stee l tests were carried out on behaviour with heart transfer. The criteri on of interpretation was first of all the weight loss rate per unit ar ea. Furthermore, the specimens are visually estimated and metallograph ical examined. Polyacrylates and copolymeres alone do not sufficient r etard the corrosion of unalloyed steel in soft storage reservoir water . A distinguished inhibition effect is obtained by simultaneous additi on of molybdate and phosphonate. A further addition of copper inhibito rs on basis of tolyltriazole renders possible the mixed installation o f unalloyed steel, copper and AlMgSi0.5 in half-open circuits. The wei ght loss rate of unalloyed steel was diminished to values <0.01 mm/a. The dependence of the weight loss rate on temperature (35/60 degrees C ) and flow velocity (0.5 to 2 m/s) is small. The weight loss rate of c opper is diminished to <0.0001 mm/a. The weight loss rate of AlMgSi0.5 with and without inhibitor is about 0.003 mm/a. By visual estimation and metallographic examination local corrosion could not be determined . The behaviour of unalloyed steel with heat transfer from the metal t o the inhibited medium is characterized by an increase in weight loss rate.