<p>In this work, a cerium-containing composite conversion film has been prepared on the PbSb alloy to improve&#xa0;its corrosion resistance. Batch studies have been carried out to address the influence of various process parameters. Systematic investigations were conducted to elucidate the film formation mechanism and evaluate the corrosion resistance property. The morphology and chemical composition were characterized with scanning electron microscopy, fourier transform infrared and x-ray diffractometry. The corrosion resistance of the samples has been measured by electrochemical and immersion tests. The results show that with the increase in the concentrations of H₂SO₄, (NH₄)₄Ce(SO₄)₄ and polyvinylpyrrolidone PVP_k30, as well as the treatment temperature, the corrosion resistance of the film first increases and then decreases slightly. The film quality is greatly influenced by the processing time. Cracks begin to appear in the film after 12&#xa0;h. Both PVP_k30 and cerium ions act as synergistic surface modifiers; as a result, the film formed under the relative optimum process is very compact and completely covered the substrate. The film, mainly composed of PbSO₄ with trace amounts of oxides, cerium compounds and organic materials, exhibits significantly superior corrosion resistance compared to the bare alloy in a carbonic acid solution.</p>