Advances in Chemical and Structural Characterization of Concretion with Implications for Modeling Marine Corrosion

Authors

Donald L. Johnson, National Park Service Submerged Resources CenterFollow
Robert J. Deangelis, 23 Balmoral Drive, Niceville, FL 32578, USA
Dana J. Medlin, Engineering Systems Inc.
James D. Carr, University of Nebraska - LincolnFollow
David L. Conlin, National Park Service Submerged Resources Center

Document Type

Article

Date of this Version

2014

Citation

JOM, Vol. 66, No. 5, 2014

Comments

© 2013 The Minerals, Metals & Materials Society

DOI: 10.1007/s11837-013-0806-x

Abstract

The Weinsnumber model and concretion equivalent corrosion rate methodology were developed as potential minimum-impact, cost-effective techniques to determine corrosion damage on submerged steel structures. To apply the full potential of these technologies, a detailed chemical and structural characterization of the concretion (hard biofouling) that transforms into iron bearing minerals is required. The fractions of existing compounds and the quantitative chemistries are difficult to determine from x-ray diffraction. Environmental scanning electron microscopy was used to present chemical compositions by means of energy-dispersive spectroscopy (EDS). EDS demonstrates the chemical data in mapping format or in point or selected area chemistries. Selectedarea EDS data collection at precise locations is presented in terms of atomic percent. The mechanism of formation and distribution of the iron-bearing mineral species at specific locations will be presented. Based on water retention measurements, porosity in terms of void volume varies from 15 v/o to 30 v/o (vol.%). The void path displayed by scanning electron microscopy imaging illustrates the tortuous path by which oxygen migrates in the water phase within the concretion from seaside to metalside.