Abstract: Gaseous pollutants formic acid (HCOOH) and acetic acid (CH₃COOH) are both significant causes of corrosion for lead-based artifacts in a museum setting. However, their corrosion processes and the types/morphology of the resulting corrosion products differ markedly. Corrosion tests were conducted on lead samples in simulated acid-free, formic acid, and acetic acid environments under varying humidity levels. The corrosion processes and mechanisms of lead in different environments were analyzed based on indicators such as mass change, glossiness, corrosion morphology and corrosion product phase. The results demonstrate that both formic acid and acetic acid exhibited significant corrosiveness towards lead across a range of humidity levels, with acetic acid causing particularly severe corrosion. Both acids attacked the PbO passivation layer on the lead surface, forming lead formate Pb(HCOO)₂ and lead acetate Pb(CH₃COO)₂. Lead acetate readily converted to loose lead carbonate, releasing acetic acid, thus establishing a cyclic corrosion process. In contrast, lead formate formed a compact crystalline structure that offered some protection to the substrate at low-to-medium humidity levels (≤75% relative humidity). However, its corrosiveness remained significantly higher compared to the acid-free environments. Consequently, the use of display and storage materials that emit formic acid or acetic acid must be strictly avoided in the preservation and exhibition of lead-based artifacts.