Abstract: Evaluation of a neutralization method and the degree of corrosiveness of disinfectants is a
crucial initial step that precedes biocidal agents efficacy study. One of the major factors affecting the choice of
the disinfectants is their aggressiveness towards materials of construction in the pharmaceutical facility. Two
dilutions of each of four commercially used peroxygen/Ag+-based disinfectants were examined against four
Gram-negative microorganisms using Fluid Thioglycolate Medium (FTM) broth for both chemical and physical
neutralization. The acceptance criteria of a test group was > 70 % of the control group for each replicate group
namely neutralizer efficacy and neutralizer toxicity. Statistical analysis using One-way analysis of variance
(ANOVA) was carried out to confirm success/failure of a suspect result. By this analysis; five suspect treatments
passed the neutralizer efficacy test. Modified FTM-thiosulfate (FTMT); FTM neutralizer, was tested under the
same conditions against the same index of microorganisms and compared to a previously used and tested FTM
neutralizer. Neutralization of the modified FTM neutralizing broth was more effective than the previously
reported FTM with peroxygens/Ag+ disinfectants especially 1:100 dilution. Using higher dilutions has minimized
the reaction time in the present study. In addition, a gravimetric corrosion test was performed to determine the
degree of corrosiveness of disinfectants. Bixco showed greatest corrosion rate when compared with other
commercially used peroxygens which were not significantly different from the control. Corrosion test is a useful
tool to determine the preference among a range of disinfectants especially if they belong to the same class.