Abstract
A small commercial cooling tower, equipped with control instruments, was installed in the laboratory for studying corrosion problems. In this tower the pH of the recirculating water was rigidly controlled automatically, and test coupons, nipples, and NDHA coil type units were used simultaneously to determine corrosion rates. Initial data revealed reasonably good correlation between corrosion rate measurements using all three types of corrosion test specimens. Inorganic corrosion inhibitors such as chromates, polyphosphates, and combinations of the two, when used in the experimental tower, provided corrosion protection comparable to that found in the field with those inhibitors. Therefore, it may be assumed that corrosion inhibitors which are successful in the experimental tower will be equally effective in field operations.
It was apparent that corrosion inhibitors such as polyphosphates must be fed in larger dosage than were required residually in the cooling water, to adequately protect against corrosion. Under operation conditions of the experimental tower, three or four times the calculated quantity of polyphosphate was required in order to maintain the desired residual dosage in the tower water.
Operating data from several inhibitor runs are reported and compared with observed corrosion rates in untreated (blank) runs. 2.3.4
