Evaluations of Long-Term Seawater Corrosion Specimens and Electrochemical Studies of Nickel Aluminum Bronze Alloys

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Authors
  1. Wang, Y.
Corporate Authors
Defence R&D Canada - Atlantic, Dartmouth NS (CAN)
Abstract
Cast nickel aluminum bronzes (NAB) are widely used in submarine seawater handling systems. However, they are susceptible to corrosion, especially selective phase corrosion (SPC), at welds and under marine growth. This leads to high repair or replacement costs. A first step in reducing these costs is to understand the effect of local environmental factors. In order to assess local environmental factors affecting the corrosion performance of NAB alloys, a long-term seawater exposure experiment was conducted. Four sets of NAB castings, including welded specimens, were immersed in natural seawater in Bedford Basin, Nova Scotia for 7, 13 and 39 months. Corrosion performance was evaluated through visual inspection, weight loss and cross-section metallographic examination. In addition, electrochemical techniques were used to study the effect of decaying biological matter on the corrosion behaviour of NAB castings. This technical memorandum presents the analysis results of the long-term exposure experiments including general corrosion and SPC in the weld heat-affected zone and under crevices formed by nylon nuts and bolts, along with local environmental conditions (dissolved oxygen, temperature, and salinity). The electrochemical study on the effect of decaying biological matter on the corrosion behaviour of NAB alloys is also presented and discussed.

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Report Number
DRDC-ATLANTIC-TM-2008-256 — Technical Memorandum
Date of publication
01 Dec 2008
Number of Pages
52
DSTKIM No
CA032129
CANDIS No
531263
Format(s):
CD ROM

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