Tribasic lead sulfate bonding

Stabilizers are almost invariably added to PVC to improve its heat and light stability. The species found effective in stabilizing PVC are those that are able to absorb or neutralize HCl, react with free radicals, react with double bonds, or neutralize other species that might accelerate degradation. Lead compounds, such as basic lead carbonate and tribasic lead sulfate, and metal soaps of barium, cadmium, lead, zinc, and calcium are used as stabilizers. Obviously, they can react with HCl. Epoxy plasticizers aid in stabilizing the resin. Another group of stabilizers are the organotin compounds, which find application because of their resistance to sulfur and because they can yield crystal-clear compounds. 

Tribasic and tetrabasic lead sulfate crystals (3Pb0PbS04-H20 and 4Pb0PbS04-xH20) contain water and are partly hydrated (x in the 4BS formula is a variable with a value between 0.18 and 0.16, i.e. 4BS crystals are superficially hydrated) [17]. PbO in the CL2 layer is hydrated, too. It can be expected that bonding between 3BS or 4BS particles of the paste and of the corrosion layer will occur by an interaction between their hydrated layers. 

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