# Evaluating the Impact of Artificial Saliva Formulations on Stainless Steel Integrity
## 3 Results and Discussion
### Morphological and Chemical Composition
Table 1 presents the X-ray fluorescence (XRF) results for 316 stainless steel (an Fe-Cr-Ni-Mo alloy) that were compared before exposure (initial) and after 7 and 28 days of immersion in three artificial saliva solutions: Afnor (pH 7.64, neutral/slightly basic), Fusayama/Meyer (pH 6.34, mildly acidic), and Fletcher (pH 8.07, basic with fluoride). The focus is on changes in key alloy elements--iron (Fe), chromium (Cr), nickel (Ni), molybdenum (Mo), copper (Cu), and cobalt (Co)--to infer corrosion or leaching behavior under each condition. Elemental changes have been highlighted to emphasize surface interactions. Slight decreases in Fe and Cr, particularly in the Fletcher samples, suggest possible leaching or passive-layer disruption. The Co and Mo showed slight increases, indicating possible surface enrichment or stabilization. The presence of P in all of the exposed samples points to ionic adsorption from the artificial saliva, especially in fluoride- and phosphate-containing environments. Table 2 summarizes the approximate compositional changes, followed by detailed interpretations for each environment. For the Afnor artificial saliva (Neutral pH 7.6), the 316 steel initially contains \(\sim\)67-68% Fe, \(\sim\)17% Cr, \(\sim\)12-13% Ni, \(\sim\)2% Mo, and only trace levels of Cu and Co (in the order of 0.1% or less). These are typical levels for 316 stainless steel, with Fe as the balance and Cr, Ni, and Mo as major alloying elements that form a passive oxide film (rich in Cr\({}_{2}\)O\({}_{3}\) with Mo oxides) for corrosion resistance. Seven-Day Exposure: After 1 week in Afnor saliva (near-neutral pH, containing chloride, phosphate, bicarbonate, and thiocyanate ions),  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \multirow{2}{*}{**Element**} & \multirow{2}{*}{**Initial Sample (\%)**} & \multicolumn{2}{c}{**Afnor Saliva (\%)**} & \multicolumn{2}{c}{**Fusayama/Meyer Saliva (\%)**} & \multicolumn{2}{c}{**Fletcher Saliva (\%)**} \\ \cline{3-7}  & & **7 Days** & **28 Days** & **7 Days** & **28 Days** & **7 Days** & **28 Days** \\ \hline Fe & 67.920 & 67.770 & 67.840 & 67.860 & 67.850 & 67.640 & 67.840 \\ Cr & 17.167 & 17.105 & 17.  
the XRF shows very minor changes. Fe remains about the same (within 0.1-0.2% of the initial \(\sim\)67.8%), and Ni and Cr also stay essentially unchanged (changes in the order of a few hundredths of a percent). Any differences at 7 days are near the margin of error, indicating minimal general corrosion in this solution. The passive Cr-oxide film likely remains intact, preventing significant metal leaching. Twenty-Eight-Day Exposure: By 28 days, the Afnor-exposed sample still shows only slight shifts in composition relative to the initial immersion. The Fe content decreases by only a few tenths of a percent (still \(\sim\)67.5-67.6%), and Ni shows a similarly tiny decrease (in the order of 0.1%). Cr conversely appears to increase slightly (to \(\sim\)17.2%, a few tenths higher than initial). This subtle Cr enrichment with a correspondingly slight Fe/Ni reduction suggests that any corrosion that did occur was extremely mild and selective--the more active elements, such as the Fe (and to some extent the Ni), may have leached in minute amounts, leaving the surface enriched in Cr [19]. Such Cr enrichment is expected because chromium is less readily dissolved--it stays behind as part of the protective oxide film, which raises the measured Cr fraction at the surface as other elements depart [20]. Mo remains roughly constant or is up by a negligible amount (\(\sim\)2.2% vs. 2.1% initially), indicating it too is retained in the passive film. Trace Cu and Co show no meaningful change (both remain at or near their initial \(\sim\)0.2% and \(\sim\)0.06% levels, respectively), which is not surprising given their very low levels--any slight dissolution or concentration is within the bounds of experimental noise. Interpretation: Overall, Afnor saliva (pH -7.6) has a negligible corrosive impact on 316 stainless steel over 28 days.