Preparation and Application of Some Metallic Nanoparticles Capped by Surfactants as Corrosion Inhibitors for Carbon Steel

Abstract

The thesis deals with preparation and application of novel surfactants as corrosion inhibitors for carbon steel in 1.0 M HCl. In addition improving the protection efficiency of epoxy paint for carbon steel by surfactants capped by nano particles. This work contains three chapters: Chapter (1): Introduction It contains of -3- essential sections. A. An introduction about corrosion (definition, types and classification). B. An introduction about surfactants (definition and classification). C. It includes the common methods for prevention steel corrosion, introduction about coating, introduction about nanotechnology and nano particles. Chapter (2): Materials and experiment techniques It includes complete description of chemicals used, preparation of solutions, metal composition and synthesis of inhibitors as the following: 1. Synthesis of novel surfactant. A. Synthesis of (1-DMBT). The tested inhibitor, namely 1-dodecyl-methy1-1H-benzo[d]-[1,2,3] triazole-1-ium bromide was synthesized from reaction of one mole 5-methyl-1H-benzo[d][1,2,3] triazole with one mole 1-bromododecane in ethanol at 70C for 24h. B. Synthesis of three tetrachlorometallate surfactant complexes (HDCo, HDMn, HDZn). These inhibitors, namely hydrazine-bis (dodecylamine)-bis (tetrachloro-metallates) have been successfully synthesized by solid state reaction by mixing and grinding dodecylamine monohydrochloride with hydrazine dihydrochloride in the absence and presence of anhydrous metal chlorides of ZnCl2, MnCl2 and CoCl2. 2. Preparation of zinc nanoparticles (ZnNPs). ZnNPs were prepared by chemical reduction of ZnCl2 solution in the presence of synthesized novel surfactants [(1-DMBT) or (HDZn)]. 3. Chemical structure of the prepared (1-DMBT) was confirmed by 1H NMR, FTIR and 13C NMR spectroscopes. 4. Characterization of the synthesized tetrachlorometallate surfactant Complexes (HDX) was carried out by (TGA), (XRD), UV- VIS spectra, atomic absorption and Raman spectroscopic. 5. Description of corrosion testes which used to evaluate the inhibition efficiency of the prepared inhibitors for carbon steel in 1.0 M HCl. 6. Applications of the unmodified and modified epoxy and performance of these paints in 3.5wt % NaCl solution by different techniques. Chapter (3): Results and discussion It is divided into four sections. Section (A): 1. Characterization of the synthesized surfactant (1-DMBT) by FTIR, 1H NMR, 13C NMR spectroscopy. 2. The Surface active properties of the surfactant were evaluated. The surface tension of the prepared surfactant decreased with an increase in its concentration up to the (Ccmc), the values of effectiveness (πcmc), maximum surface excess (Γmax) and minimum surface area (Amin) were calculated. 3. The adsorption of surfactant on carbon steel obeyed the Langmuir adsorption isotherm. Thermodynamic parameters for adsorption process such as free standard energy (∆Gοads), enthalpy (ΔHoads) and entropy (ΔSoads) of the (1-DMBT) were calculated. The negative values of (∆Gοads) indicate that the adsorption of (1-DMBT) on the metal surface is a spontaneous process. The negative value of (ΔHoads) indicates the adsorption is exothermic process. The positive sign of (ΔSoads) is attributed to an increase of disorder due to the adsorption of only one surfactant molecule by desorption of more water molecules. 4. The prepared (1-DMBT) was investigated as corrosion inhibitor using different techniques: i. Weight loss measurements The data revered that, the inhibition efficiency of synthesized (1-DMBT) increased with increasing its concentration and decreased with temperature. ii. Potentiodynamic polarization measurements The data indicated that by increasing the inhibitor concentration the inhibition efficiency increased. The results suggested that inhibitor species may be adsorbed on the steel surface and cover some active sites of the electrode surface. iii. Electrochemical impedance spectroscopy (ElS) (a) Nyquist plots The data showed that an increase of charge transfer resistance and a decrease of double layer capacitance with increasing the inhibitor concentration related to formation of a barrier surface film.

(b) Bade plots The increase of absolute impedance at low frequencies confirmed the higher protection with increasing the concentration of (1-DMBT). The results obtained from the weight loss measurements were in good agreements with those obtained from potentiodynamic polarization method and electrochemical impedance spectroscopy (ElS) method.