A parametric test program involving completion alloys in supercritical CO2 was conducted using both isothermal and non-isothermal cycles in the presence of contaminants (i.e., H2O, NO2, SO2, H2S, H2) above typical impurity limits for carbon capture and sequestration (CCS). The isothermal testing consisted of 4500 psi (310 bar) autoclave tests at 175°F (79°C) with the test materials in supercritical CO2, and optionally, in a NaCl-rich brine in equilibrium; the non-isothermal testing was similar, but included three consecutive cycles with 250°F (121°C) and 70°F (21°C) exposures. Up to ten corrosion-resistant alloys [i.e., 9Cr (UNS K90941), 13Cr (UNS S42000), S13Cr (ISO13680 (1) Type 13-5-2), 15Cr (proprietary), 17Cr (proprietary, 22Cr (UNS S32205), 25Cr (UNS S32750), G3 (UNS N06985), 925 (UNS N09925), 718 (UNS N07718), and 716 (UNS N07716)] were tested for weight loss, pitting, and crevice corrosion. The alloys, known to be more susceptible to environmentally-assisted cracking (EAC), were also evaluated for cracking with ppm-levels impurities (25-to-150 ppmv each), including hydrogen sulfide (H2S). Alloys 22Cr, 25Cr, and API (2) Spec. 6A and Std. 5CRA nickel-based alloys are generally found to be fit-for-service for subsurface CCS. In contrast, the alloys with 9-to-17 wt.% chromium tend to suffer from pitting, which when extensive, has been associated with a case of EAC. For the pitting-resistant alloys under test, neither EAC nor crevice corrosion created major new risks. The introduction of non-isothermal cycles to qualify alloys for CCS has successfully emphasized the dominant effects of condensates, otherwise under-represented, and is suggested for future material testing and qualification programs.