Abstract
The marine biofouling and corrosion of Kunifer 10 (10% Ni, 1. 5% Fe, copper alloy), was studied using a combination of analytical techniques including x-ray photoelectron spectroscopy (XPS), energy dispersive x-ray analysis (EDXA) and electron microscopy. Particular emphasis was placed on the very early stages of fouling, although the study continued until a climax community of macrofouling organisms had become established. Dissolved organic matter (DOM), was successfully extracted from seawater by ultrafiltration and chloroform-emulsion separation. The collected materials were partially characterised using fourier transform infrared spectroscopy (FTIR) and standard chemical analyses. Extracted materials were found to be mainly carbohydrate in character, with lesser quantities of protein. The FTIR investigations indicated considerable seasonal variation in the extracted DOM. XPS proved to be a suitable technique to investigate the development of marine organic and inorganic films that form on the alloy. Adsorbed organic macromolecules exhibited a characteristic spectral "fingerprint". The effect of elevated DOM on the corrosion behaviour of the Kunifer 10 alloy was investigated, using DC and AC impedance electrochemistry. Studies indicated that a temporary loss of passivation occurred in the presence of DOM under transient oxygen conditions. The development of organic layers on the alloy was shown to influence subsequent stages of biofouling, Kunifer 10 coated with elevated levels' of organic extracts was less likely to become fouled by microorganisms, although certain extracts appeared to stimulate the settlement of marine protozoans. However, such effects were short lived due to the continual formation of bio/corrosion layers. An unusual form of corrosion, not previously documented, is reported and an explanation for the exfoliation of the bio/corrosion films on Kunifer 10 is suggested. A range of cupronickel-iron alloys were assessed for their short-term marine biofouling/corrosion performance. Of the alloys tested Kunifer 10 showed optimum resistance. The study includes a literature review on marine biofouling and corrosion.