When purchasing lead in bulk, the most critical factor is purity levels, typically required at 99.97% or 99.99% (Pure Lead) for battery and chemical applications. For industrial use, specify the alloy composition (e.g., Antimonial Lead for hardness). Ensure the supplier provides a Material Test Report (MTR) or a Certificate of Analysis (COA) that details the concentration of impurities like bismuth, copper, and silver, as these affect the metal's electrochemical performance and corrosion resistance.