Protection of beryllium metal against microbial influenced corrosion using silane self-assembled monolayers
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I. INTRODUCTION
BERYLLIUM has attractive physical, chemical, and mechanical properties, including a low density (1.85 g/cc), a relatively high melting point (1289 8C), a low neutroncapture cross section, a high specific heat and thermal conductivity, a high modulus of elasticity (one-third greater than that of steel), and a good retention of mechanical strength at elevated temperatures. Beryllium is therefore used in a number of applications in the chemical, nuclear, and structural industries. Beryllium also has adequate corrosion resistance for use in many engineering applications due to the formation of a protective oxide film when exposed to air. This surface film is either BeO ˚ or its hydrate (BeO ? (H2O)x) and is on the order of 20 A in thickness (in aqueous chloride solutions).[1] The oxide layer formed on the surface of beryllium is resistant to cracking or spalling because it is in a state of compression (due to its larger volume).[2] Recent studies[1–5] to evaluate the corrosion resistance of beryllium have documented the behavior of beryllium in a variety of aggressive environments. All of these studies have shown that beryllium is susceptible to pitting corrosion.[1–5] This breakdown of passivity in beryllium occurs at localized sites in a stochastic manner. Pitting corrosion of beryllium can severely compromise its mechanical properties.[6] Although the corrosion of beryllium in aqueous environments has been well established,[1] we are not aware of any RAJENDRA U. VAIDYA, Technical Staff Member, Materials Science Division, and ALINA DESHPANDE and LARRY HERSMAN, Technical Staff Members, Life Sciences Division, are with Los Alamos National Laboratory, Los Alamos, NM 87545. SUSAN M. BROZIK, formerly Technical Staff Member, Nuclear Materials Technology Division, Los Alamos National Laboratory, is with the Sandia National Laboratory, Albuquerque, NM 87047. DARRYL BUTT, formerly Technical Staff Member, Materials Science Division, Los Alamos National Laboratory, is with Ceramatec, Salt Lake City, UT 84119. Manuscript submitted October 27, 1998. METALLURGICAL AND MATERIALS TRANSACTIONS A
study documenting the microbiologically influenced corrosion (MIC) of beryllium. Numerous applications (both structural and nonstructural) and scenarios involving beryllium exist[7,8,9] where MIC potentially could compromise the mechanical properties of the material. Microbiologically influenced corrosion has been identified and studied for over 100 years,[10–16] and its effect on the mechanical properties of different materials has also been documented.[17,18] It is even more important to investigate MIC effects on beryllium because of beryllium’s known susceptibility to pitting, which is almost always an outcome of the MIC process. The first goal of our study was to determine the effect of MIC on the mechanical response of beryllium. Having established, through this study, that MIC does compromise the mechanical properties of beryllium, we were interested in pursuing the application of self-assembled monolayers (SAMs) as c
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