Interaction between various metals and the hydrozoan millepora dichotoma in a coral-reef environment

Small fragments of the hydrocoral, Millepora dichotoma, were glued to PVC racks containing three different types of metals. The following groups of metals were deployed: electrochemically passive metals - UNS S30403, UNS S31603, UNS S31254, UNS R50400, UNS R52400, UNS R53400 and UNS N10276; electrochemically active metal with no harmful biological effect - St-37 mild steel; metals with biocidic effect - commercial copper and bras 30/70. The samples were immersed in the coral reef environment, at 6 meters depth for a period of 3 months, between May-August 2000. An adhesive two-dimensional growth of the M. dichotoma encrustation layer on the metal surface was clearly observed in all the electrochemically passive metals. No two-dimensional development of the hydrocoral was observed on the mild steel. The tips attached to the plates of commercial copper and brass 3o/70 were damaged and died within three weeks.