Corrosion Inhibition Of Stainless Steel Research Articles

Corrosion Inhibition Effect of 4-(2-Diethylamino-Ethylsulfonyl)-Phthalonitrile and 4,5-Bis(Hexylsulfonyl)-Phthalonitrile

Inhibition of stainless steel corrosion in a 3.0 M NaCl solution by 4-(2-diethylamino-ethylsulfanyl)-phthalonitrile (DAESPN) and 4,5-bis(hexylsulfonyl)-phthalonitrile (Bis-HSPN) was investigated by polarization and electrochemical impedance spectroscopy (EIS) measurements. The values of cathodic (βc) and anodic (βa) Tafel slopes, , , corrosion rate (CR), and inhibition efficiences (IE%) obtained from polarization curves and polarization resistance (), double-layer capacitance (), specific capacitance () values were obtained from EIS. Double-layer capacitance differences in the presence and absence of inhibitors were also obtained from EIS measurements as suggested in the literature in order to investigate the interaction of them with metal surface. Results show that both DAESPN and Bis-HSPN are effective in cathodic reaction. Impedance measurements suggest higher surface coverage for DAESPN. The interaction between the inhibitor and the stainless steel was investigated by the adsorption isotherm. Langmuir adsorption isotherm was applied and values were obtained and found as , and 9.2 kJ, 12.5 kJ for DAESPN and Bis-HSPN, respectively, which suggests the electrostatic interaction between charged metal surface and charged organic molecules.

Surface Analysis of Inhibitor Film Formed by Poly(Vinyl Alcohol) on Stainless Steel in Sodium Chloride Solution

The corrosion inhibition of stainless steel in 0.9% NaCl solution in presence of poly(vinyl alcohol) (PVA) is discussed according to electrochemical measurements, such as potentiodynamic polarization and electrochemical impedance spectroscopy (EIS).The morphology of the surface was analyzed using Scanning Electron Microscopy (SEM). The composition of the layer formed on stainless steel surface was estimated using X-ray Photoelectron Spectroscopy (XPS) technique. Electrochemical measurements indicated that the presence of PVA in NaCl solution decreases the corrosion current and increases the polarization resistance. The values of inhibition efficiency obtained from polarization curves and EIS measurements are in good agreement. In absence and in presence of PVA, SEM images showed that the stainless steel surface was covered with a non-uniform layer and a uniform adsorbed film, respectively. XPS analysis indicated that the surface layer consists of PVA containing a small amount of other elements, such as Na and Cl.

Poly(3-octylthiophene) and polystyrene blends thermally treated as coatings for corrosion protection of stainless steel 304

The effect of thermal annealing of poly(3-octylthiophene) (P3OT) and polystyrene (PS) blend coatings on the corrosion inhibition of stainless steel in a 0.5 M NaCl solution was investigated. P3OT was synthesized by direct oxidation of the 3-octylthiophene monomer with ferric chloride (FeCl3) as oxidant. Stainless steel electrodes with mirror finish were coated with P3OT/PS blend by drop-casting technique. In order to study the temperature effect on the function like physical barrier against the corrosive species of P3OT/PS polymeric blend, the coatings were thermally annealed at three different temperatures (55 °C, 80 °C, and 100 °C). The corrosion behavior of P3OT/PS-coated stainless steel was investigated in 0.5 M NaCl at room temperature, by using potentiodynamic polarization curves, linear polarization resistance (LPR), and electrochemical impedance spectroscopy. The LPR values indicated that, at 100 °C, P3OT/PS coatings showed a better protection of the 304 stainless steel in 0.5 M NaCl; the corrosion rate diminished in two orders of magnitude with regard to the bare stainless steel. The superficial morphology of the coatings before and after the corrosive environment was researched by atomic force microscopy, optic microscopy, and scanning electronic microscopy. Morphological study showed that the increased temperature benefited the integration of the two polymeric phases, which improved the barrier properties of the coatings. The coating/metal adhesion and the coating thickness were evaluated. The temperature increases the adhesion degree coating/substrate; thus, the coating annealed at 100 °C showed the best adhesion.

Effect of thermal annealing of poly(3-octylthiophene) films covered stainless steel on corrosion properties

The effect of thermal annealing of poly(3-octylthiophene) (P3OT) coatings on the corrosion inhibition of stainless steel in an NaCl solution was investigated. P3OT was synthesized by direct oxidation of the 3-octylthiophene monomer with ferric chloride (FeCl3) as oxidant. P3OT films were deposited by drop-casting technique onto 304 stainless steel electrode (304SS). 304SS coated with P3OT films were thermally annealed during 30 h at different temperatures (55°C, 80°C, and 100°C). The corrosion resistance of stainless steel coated with P3OT in 0.5 M NaCl aqueous solution at room temperature was investigated by using potentiodynamic polarization curves, linear polarization resistance, and electrochemical impedance spectroscopy. The results indicated that the thermal treatment at 80°C and 100°C of P3OT films improved the corrosion resistance of the stainless steel in NaCl solution; the speed of corrosion diminished in an order of magnitude with regard to the 304SS. In order to study the temperature effect in the morphology of the coatings before and after the corrosive environment and correlate it with corrosion protection, atomic force microscopy and scanning electron microscopy were used. Morphological study showed that when the films are heated, the grain size increased and a denser surface was obtained, which benefited the barrier properties of the film.

Corrosion inhibition of stainless steel by polyaniline, poly(2-chloroaniline), and poly(aniline- co-2-chloroaniline) in HCl

Polyaniline (PANi), poly(2-chloroaniline) (PClANi), and poly(aniline- co-2-chloroaniline) ( co-PClANi) films were synthesized by electrochemical deposition on 304-stainless steel (SS) from an acetonitrile solution. The structural properties of these polymer films were characterized by spectroscopic (FTIR and UV–vis) and electrochemical (cyclic voltammetry) methods. Open circuit potential–time ( E ocp–time) curves, potentiodynamic polarization, and electrochemical impedance (EIS) measurements showed that these films have significant protective performance against corrosion of SS in 0.5 M HCl solution. It was found that co-PClANi film has acted as a passivator as well as barrier for cathodic reduction reaction in a similar manner as PANi film. However, PClANi film has behaved only as barrier for corrosion protection of SS in 0.5 M HCl.

Study of the reaction of lanthanum nitrate with metal oxides present in the scale formed at high temperatures on stainless steel

The reaction of lanthanum nitrate with metallic oxides that can be present in the oxide scales formed at elevated temperatures on the surface of stainless steel has been investigated as model systems of the processes occurring during the oxidation of lanthanum coated stainless steel. X-ray diffraction (XRD) experiments have shown that LaCrO3 and LaFeO3 are the most stable compounds. XRD, chemical analysis and thermogravimetric experiments have demonstrated that in the case of Cr2O3, nitrate anions are able to oxidize Cr(III) to Cr(VI) resulting in a precursor phase of perovskite structure that influences the corrosion inhibition of stainless steel at high temperatures.

Corrosion inhibition of structural steels in the carbon dioxide absorption process by 1-(hydroxyethylidene)-1,1-diphosphonic acid

Corrosion inhibition of stainless steel (type 304, (UNS S30400)) and mild steel (SS 41 (UNS K02600)) in the CO 2 absorption process was investigated by corrosion tests and physicochemical measurements in an aqueous potassium carbonate solution containing 1-(hydroxyethylidene)-1,1-diphosphonic acid (HEDP). The maximum value of the inhibition efficiency (η) of corrosion for SS 41 was ca. 80% in the test solution containing 200 ppm of HEDP under air atmosphere by the corrosion weight loss test and approached those values obtained in the test solutions with Na 2 CrO 4 (>99%) and V 2 O 5 (>99%). The corrosion rate result obtained with the corrosion weight loss test corresponded to that obtained with electrochemical measurements. By scanning tunneling microscopy (STM), the molecules of HEDP were adsorbed on the surface of SS 41 to inhibit its corrosion. In the application test, using a Benfield apparatus as a bench-scale system, the η value for type 304 was ca. 80-90% in the test solution containing HEDP at high pressure and temperature. The HEDP also depressed the formation of scale as well as depressed the result in the water-cooling process

Mechanism of the Corrosion Inhibition of Stainless Steel in Sulfuric Acid by Sodium Molybdophosphate

Sodium 12‐molybdophosphate inhibits the corrosion of an actively corroding type 430 stainless steel sample in sulfuric acid by first polarizing the sample to the primary passivation potential. After this potential is reached, the stainless steel sample passivates spontaneously. From the potentiodynamic polarization curves it was deduced that the addition of sodium molybdophosphate to the sulfuric acid does not significantly alter the anodic characteristics of the type 430 steel in sulfuric acid. The experimental results were in agreement with the electrochemical theory for the passivator‐type inhibitors.