The corrosion protection and/or adsorption of polyacrylamide (PAA) of number average molecular weight, n M , between 15,000 -1,350,000 g mol -1 on mild steel and iron (99.99 % Fe) in 3 M HCl at room temperature was studied using spectrophotometry (the phenanthroline method), the weight loss method and EIS (Electrochemical Impedance Spectroscopy). It was found that the corrosion protecttion efficiency of the PAA -adsorbed layers strongly depends on both the molar concentration of PAA in the solution and its molecular weight, reaching limiting values between 85 and 96 %. Simultaneously, it was also concluded that a relatively high surface coverage could be obtained with very low PAA concentrations (0.5 -2 ppm), indicating the good adsorption characteristics of PAA on mild steel and iron in hydrochloride acid. The experimentally obtained results follow a Langmuir adsorption isotherm. According to the best fitting parameters, the adsorption coefficient B ranged between 2×10 7 and 4×10 8 mol -1 and depended strongly on the molecular weight of the PAA: B = k α n M (for α ≈ 0.67 and k = 2.95×10 4 ) or the size of the polymer coil. As was found by EIS, the thickness of the adsorbed PAA layer was approx. 1.1 nm (for ε r = 15) and corresponded only to the polymer segments attached to the metal surface. On the other hand, as was found by ellipsometry, the limiting layer of the adsorbed PAA molecules was highly voluminous and relatively thick (100 -200 nm), containing entangled polymer coils.
SYNOPSISObtaining a "hybrid" electroconductive polymer composite material on the basis of a fibrous carrier and polypyrrole (pPy) was studied. As fibrous carriers, polyacrylonitrile (PAN) and chemically modified polyacrylonitrile possessing ion-exchange properties were used. FeCl,, chosen as an initiator for oxidative polymerization of pyrrole (Py), was introduced in the fibrous matrix by sorption from an aqueous or diethylether solution. The polypyrrole film was deposited onto/in a matrix prepared in this way by polymerization of pyrrole in a vapor phase, from t h e vacuum, or from a solution of Py in toluene. In some cases, an additional doping of the obtained (electroconductive) pPy film, with iodine vapors in the vacuum, was also applied. An electroconductive composite material, with volume resistivity of about 10 Q cm, was obtained. The results, related to the different nature of the fibrous carrier and different procedures for the oxidizer introduction or pPy deposition, were discussed. 0 1996 John Wiley & Sons, Inc.
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