Copolymer of acrylamide and 4-vinyl pyridine (CPAV)

which had been synthesized by radical copolymetization in solution of DMF／water(volume／volume=1:1) using potassium persulfate as initiator

was quaternarized using dimethyl sulphate

and a series of copolymers having pendent quaternary pyridinium group have been synthesized

which have different degree of cationization and different molecular weight．The cationic copolymerwas characterized by FTIR

13C-NMR and UV analysis and its flocculation and corrosion inhibition properties were studied in detail．The cationic copolymers QCPAV displayed good properties in the experiments．The experimental results of flocculation for siliceous earth suspension showed that the transmittance of the supernatant layer of the siliceous earth suspension after being flocculated could come up to 100％；without need of adding any other coagulation aids．QCPAV has good flocculation effect under weak alkline condition (Optimum pH is about 8 and Optimum added amount is 1×10-6～2×10-6 g/g)

and its performance was superior to that of non-ion polyacrylamide(PAM)．The experiments results of corrosion inhibition in 0.5 mol／L sulfuric acid solution showed that QCPAV was effective for the corrosion prevention of A3 steel in sulfuric acid solution and corrosion inhibition rate to steel A3 can reach 85％．It was found that the higher the degree of cationization is

the better flocculation and corrosion inhibition functions is

and the molecular weight of the copolymers also affects these functions obviously．The research results of the flocculation mechanism showed that the reason that the QCPAV has good flocculation property is the synergistic reaction of charge neutralization and bridging absorption．In the research of corrosion inhibition mechanism

the conclusions could be arrived at that QCPAV could form a compact adsorption film on the mental surface．The formation process of the film was closely associated with the physisorption through electrostatic gravitation and the chemisorption through coordination of π electrons of pyridine and d orbit of atom Fe．