Fig. 5. Polished sections of (a) a fresh Fe⁰ filings, (b) loose Fe⁰ filing from the shallow up-gradient Core A collected after the first 15 mo of operation showing thin Fe (oxy)hydroxides corrosion rinds and aragonite crystals on the filing surface; (c) loose Fe⁰ filing from the shallow midsection of Core 1 collected 30 mo after installation showing thick Fe (oxy)hydroxide corrosion rinds from the depletion of the underlying Fe⁰ filing; (d) loose Fe⁰ filing corroding into smaller pieces from the shallow midsection of Core 1 collected 30 mo after installation; (e) scanning electron microscopy (SEM)–backscatter electron (BSE) analysis of cemented Fe⁰ filings from the up-gradient shallow Core A collected after the first 15 mo of operation; and (f) SEM–BSE of cemented Fe⁰ filings from the up-gradient shallow Core 1 collected after 30 mo of operation. [Note the smaller Fe⁰ filings and greater disintegration of the sample collected after 30 mo of operation (f) compared with the sample collected after the first 15 mo of operation (e).]