Erosion-Corrosion of Marine Alloys

Marine alloys such as stainless steels, copper-base alloys and cast iron have a
long history of applications over a wide range of industries. They always are
exposed to aggressive erosion-corrosion environments to support or transmit forces
during the service, where more than millions of pounds are involved to repair the
material degradation every year. In order to minimize this cost, lots of money and
research have been put into practice, from which more and more erosion-corrosion
behaviour and mechanisms of marine alloys were understood, however, downtime
of marine systems still happens, moreover it is still a fact that it is quite difficult to
choose the optimum material for the specific working environment.
In this project, erosion-corrosion performance of eight marine alloys which
include three different grade stainless steels, four copper-base alloys and one Niresist
cast iron has been assessed under liquid-solid jet impingement over eight sets
of test conditions in 3.5% sodium chloride solution. Firstly, the weight loss of
different marine alloys ranks the priority of their corrosion, erosion and erosion-corrosion
resistance over the range of the test conditions, furthermore the total
weight loss test, in conjunction with in-situ electrochemistry measurements, enable
the relative contribution of the different mechanisms interacting in the degradation
to be quantified, meanwhile the aspects of erosion-corrosion mechanisms of
different marine alloys have been detailed. Even erosion-corrosion is a complex
process, but microhardness has been found to be the controlling factor in severe
erosion-dominated conditions. More importantly, primary concerns have been
brought on the factorial contributions of individual environmental parameters and
their interactions to the overall material degradations. A full two-level factorial
experimental design method combined with following analysis of variance was
applied to qualify these factorial contributions, which shows effects of the individual
environmental parameters and their interactions on the weight loss during the
erosion-corrosion processes, and the prominent factors are velocity, sand loading
and their interaction. Fluid temperature has the smallest effect compared with other
environmental parameters.