Multidimensional Study On The Corrosion Inhibition of Polypyrrole-Chitosan (PPy-CTS) Composites For Carbon Steel In Acid Medium

The acidic corrosion of carbon steel is a great concern, which has caused serious economic losses on a global scale. Therefore, the exploitation of corrosion inhibition strategy for carbon steel and an in-depth study on its mechanism are of vital importance. Here we have developed a mixed type corrosion inhibitor of PPy-CTS, which incorporated the good solubility and adsorption capacity of chitosan (CTS) into the excellent corrosion inhibition performance of polypyrrole (PPy) by in-situ polymerization of pyrrole on CTS. The corrosion inhibition performance of PPy-CTS composites as a potential corrosion inhibitor for Q235 carbon steel in 1 M HCl solution was investigated by electrochemical (potentiodynamic polarization curve and AC impedance spectroscopy) and surface morphological (scanning electron microscopy and water droplet contact angle) characterization. The results revealed that PPy-CTS with the optimal concentration of 250 ppm achieved the highest corrosion inhibition efficiency of 91.1%. Subsequently, the corrosion inhibition mechanism was furtherly studied. Gibbs free energy obtained from the Langmuir isotherm model suggested that the absorption of PPy-CTS corrosion inhibitor on Q235 steel in 1 M HCl solution belonged to a combined type of physisorption and chemisorption, which resulted in the formation of a physical barrier preventing the carbon steel from corrosion. In addition, the conductive polymer PPy of corrosion inhibitor possessed an oxide-film anodic protection for carbon steel. Ultimately, PPy-CTS effectively suppressed the corrosion reaction of carbon steel in harsh acidic environment through the synergistic effect of physical barrier and anodic protection.

Anodic protection of 316L stainless steel piping in sulfuric acid service: failure causes and remedial actions

Anodic protection (AP) is one of the corrosion control methods that has been widely used in the manufacture, storage, and transport of sulfuric acid. The present paper gives a brief review of the history, some applications, and a case study of failure causes and remedial actions of AP in a sulfuric manufacturing plant. The AP system consists of a direct current source, cathodes, reference electrodes, and signal conditioning electronics. In a sulfuric manufacturing plant, for AP of 316L piping (as an anode), platinized titanium (Pt/Ti) and Hastelloy B-2 were used as reference and cathode electrodes, respectively. After seven years of operation of the AP system in the sulfuric acid plant, a section of the protected pipelines has severely corroded. The study of the system showed that the reference electrodes, which were titanium-electroplated with platinum, lost their stability in the acid with the loss of coating and caused overprotection. However, the system could not control the pipe’s potential in the AP situation. In this condition, accelerated corrosion of the cathodes and pipes has also occurred.

Issue of technological equipment corrosion at chemical wood processing enterprises (review)

The review is devoted to the problem of corrosion in the chemical processing of wood. Corrosion processes of technological equipment at enterprises of the pulp and paper, hydrolysis and wood chemical industries are considered. The influence of the main chemical substances involved in the technological process or formed during the chemical processing of wood is discussed. The importance of using alloyed, corrosion-resistant steels of grades 10Kh17N13M2T, 10Kh17N13M3T, 08Kh17N15M3T in the processes of chemical transformation is shown. The information on methods of protection of structural materials from corrosion at enterprises in recent years is presented. The prospects of industrial use of the method of anodic protection, which consists in creating a passivating film on the surface of the protected structure by anodic polarization from an external source of direct current, is noted. The importance of using inhibitors in the composition of technological media is discussed, as one of the most effective ways to combat metal corrosion in aggressive media. It is noted that in addition to the well-known inhibitors of acid corrosion KI-1, PB-5, PKU-3, KhOSP-10, urotropin, KPI-3, I-1-V, BA-6, the use of green chemistry advances is promising, in particular, the use of as anticorrosive agents for waste processing of both wood itself and corrosion inhibitors based on plant extracts.

Anodic Protection Assessment Using Alumina-Forming Alloys in Chloride Molten Salt for CSP Plants

The generation of a natural protective coating in alumina-forming alloys was analyzed using a ternary chloride molten salt as a thermal energy storage material for concentrated solar power (CSP) technology. The formation of the protective layer was monitored using electrochemical impedance spectroscopy (EIS). A protective layer model for the OCT alloy and a localized corrosion model for the OCI and OC4 alloys were obtained after 5 h of immersion. The corrosion rates calculated using the linear polarization technique (LPR), were 8.03, 21.55, and 7.61 mm/year for OC4, OCI, and OCT alloys, respectively. These results were confirmed by scanning electron microscopy and X-ray diffraction. Our analysis showed that MgAl2O4 was the main protective coating generated by the alumina-forming alloys.

Corrosion and corrosion prevention in heat exchangers

In many industries and processes, heat exchangers are of vital importance as they are used to transfer heat from one fluid to another. These fluids can be corrosive to heat exchangers, which are usually made of metallic materials. This paper illustrates that corrosion is an important problem in the operation of heat exchangers in many environments, for which no straightforward answer exists. Corrosion failures of heat exchangers are common, and corrosion often involves high maintenance or repair costs. In this review, an overview is given of what is known on corrosion in heat exchangers. The different types of corrosion encountered in heat exchangers and the susceptible places in the devices are discussed first. This is combined with an overview of failure analyses for each type of corrosion. Next, the effect of heat transfer on corrosion and the influence of corrosion on the thermohydraulic performances are discussed. Finally, the prevention and control of corrosion is tackled. Prevention goes from general design considerations and operation guidelines to the use of cathodic and anodic protection.

Pitting inhibition in fiber dyeing solutions by two oxyanions

Purpose Pitting inhibition efficiency of SO4− and NO3− on AISI 316L stainless steel in contact with Cl−-containing fiber dyeing solutions together with the influence of the anions on absorption behavior of the solutions were investigated. The purpose of the study is to experimentally determine an optimized dyeing solution efficient on both – inhibition of the steel’s pitting and exhaustion of the dyes dissolved. Design/methodology/approach Methods such as electrochemical cyclic polarization, UV-visible range spectrophotometry and scanning electron microscopy have been used to assess the performance of two inhibitors on both pitting inhibition of the steel and dissolving ability over the reactive dyes. To find out a promising dyeing solution mixture in both aspects, Cl content of the original dyeing solution was replaced gradually with the inhibiting anions, where the total anionic content was kept constant to unchange the dye exhaustion potential of the solution. Then, those solutions came out with diverse pitting inhibition, and dye absorption levels were compared together for reducing/avoiding the pitting issues of the reactive dyeing vessels of the industry. Findings Rather high absorption levels detected by visible range spectrophotometry on the solutions showing sound inhibition levels indicated possibility of unaltered reactive dyeing qualities with an enhanced vessel lifetime as the inhibitive anions replace Cl−. Nitrate performed better than sulfate both on inhibition and absorption in the dyeing solutions. Also, 316L vessels became open to an extra anodic protection in inhibitor added solutions. Research limitations/implications The findings are valid for a certain group of reactive dyes and dyeing solutions held at 70°C. However, the testing methods are available to almost any dyeing solution and dyeing temperature. Originality/value The work presents a combined testing of pitting inhibition and absorption behavior of dyeing solutions involving Cl− that has not been reported so far. It shows that solution recipes least harmful to the steel vessels can be outlined for various reactive or other types of dye groups.