Synthesis, characterization and in situ Raman detection of Sn3O2(OH)2−xClx phases as intermediates in tin corrosion

Possible intermediates in tin corrosion formed from the chemical reaction between SnIICl2 and NaHCO3 at certain pH levels were characterized. At low pH SnII21O6(OH)14Cl16 was observed. Changing pH to higher-value substitution phases of SnII3O2(OH)2−xClx with varying x were obtained. The corrosion behaviour of tin at 80 °C and 80% relative humidity was studied using a newly developed Raman cell for in situ measurements. The reaction mechanism on tin surfaces contaminated with NaHCO3 and NaCl was clarified. In the presence of chloride ions, SnII3O2(OH)2−xClx and SnIIO were observed prior the SnIVO2 formation, whereas SnII3O2(OH)2 was detected in the absence of chloride.