Improved Instrumentation For Oceanic Fouling Forecasts

Small, portable, inexpensive flow cells have been developed to allow rapid characterization of the microbiological fouling and scaling of engineering materials proposed for seawater duty (U.S. Patent No. 4, 175,233, Flow Cell and Method for Continuously Monitoring Deposits on Flow Surfaces). Typically, multiple units are manifolded into an array conducting ocean water (unmodified or treated with various antifouling agents) through the test cells, which are then removed from the system at pre-scheduled intervals. The two flat test plate surfaces contained in each cell are analyzed by the techniques of infrared spectroscopy, ellipsometry, contact potential, contact angle determination, scanning electron microscopy, and energy dispersive x-ray techniques. The analyses reveal the initial fouling layer composition, thickness, and morphology through time. Additional data from continuous measurements of heat transfer degradation, as the fouling process takes place, are available with specially designed flow cells of similar type. It has been found, in tests with diverse seawaters and brackish waters, that the microfouling events are usually initiated by spontaneous adsorption of humic-like films that are secondarily colonized by pioneer microorganisms; film build-up continues through secretion of cellulosic slimes, proliferation of filaments, and entrapment of particulate debris. The latter events can be suppressed when toxic copper materials are used or antifouling chemicals (e.g., chlorine) are added. In some cases, iron-rich precursor slimes have been found to potentiate build-up of porous silicate overlayers that seriously impair heat transfer efficiency. Thus, evaluation of various material/water/treatment combinations can be carried out quickly and economically with these simple devices.