CREVICE AND GALVANIC ATMOSPHERIC CORROSION TESTING OF CONTROL AND PROTOTYPE STEELS

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2024

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The United States Navy aims to develop new high strength steels with superior mechanical properties for naval applications. A novel nickel-based steel is being researched as a suitable candidate to replace currently used high strength steels. As an emerging steel alloy, it is necessary to evaluate its corrosion performance which may vary depending on the composition and environment. This research investigated four steels consisting of a control steel, HY-100, and three prototype steels of a modified HSLA, 10Ni QQT, and 10Ni QQLT. Material characterization of the steels was conducted through an analysis of the steel microstructure utilizing metallography, and a study of the corrosion behavior via electrochemical polarization. Metallographic imaging revealed the microstructural characteristics of the steels. Microstructural morphologies were identified, along with an observed reduction in grain size of the 10Ni steels relative to the HY-100 and HSLA steels. Potentiodynamic polarization testing provided an estimation of the corrosion rates of each steel in three different solutions simulating freshwater, acidic, and saline environments. Acidic environments of pH 3 proved to be the most corrosive towards the steels. Furthermore, the galvanic corrosion of the steels coupled to nickel aluminum bronze (NAB) and low voltage aluminum (LV Al) was investigated. LV Al had minimal galvanic effect on the steels in the pH 3 solution, but was effective in promoting cathodic protection in the neutral solutions in certain conditions. However, the galvanic coupling of NAB displayed significant galvanic corrosion rates of the steels in aerated conditions.

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Mechanical engineering, Materials Science, Naval engineering, Corrosion, Crevice corrosion, Engineering, Galvanic corrosion

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138 pages

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