Papers by Keyword: Inhibitors

Abstract: The recrystallization and inhibitor precipitation behaviors of rare earths under water cooling after holding for different times of oriented silicon steel hot rolled at 1200°C in the ferrite zone with 30% deformation were analyzed using Gleeble 1500D, SEM,TEM and ICP. The results showed that: during the hot rolling of oriented silicon steel in the high temperature ferrite zone, only dynamic reversion occurred, no dynamic recrystallization occurred, and the amount of precipitates did not increase significantly; after deformation at 1200°C, static recrystallization occurred after holding for about 20s, and the inhibitor started to precipitate and grow. The higher the recrystallization rate, the faster the volume fraction of precipitates. After the deformation, the amount of Cu₂S and MnS in the precipitates was similar. At 64% recrystallization rate, MnS increased by about 8% and Cu₂S increased by about 23%. At the same time, most of the precipitates were precipitated in the crystal, and gradually nucleated and grew at the grain boundary when the holding time was extended. After rare earth lanthanum and cerium were added, the precipitation amount of inhibitor was reduced. The higher the degree of static recrystallization, the more obvious the effect of rare earth on the precipitation of inhibitor.

Abstract: In this work, imidazoline-oleic derivative had been successfully synthesized by reacting ethylenediamine (EDA) with oleic acid (OA). The synthesis process was performed with MAOS (Microwave Assisted Organic Synthesis) and the conventional method (reflux with Dean-Stark) using xylene as a solvent was also performed as comparisons. The percentage yield of EDA-OA imidazoline was obtained from Reflux with Dean-Stark at 5 hours (90 %), and MAOS at 10 min (68,2 %). EDA-OA imidazoline then was identified by using thin-layer chromatography, and the separation method by KVC with eluent CHCl₃: MeOH (9:1) with ammonium solution followed by characterization using Fourier Transform Infrared (FTIR), UV-Vis, Proton Nuclear Magnetic Resonance (¹H-NMR). This study provides information regarding the comparison method for imidazoline derivative synthesis. For further research, EDA-OA imidazoline can be used as a corrosion inhibitor towards carbon steel.

Abstract: In this study, mild steel was treated with SDBS:ZnSO₄ compound by immersing the mild steel substrates in a SDBS:ZnSO₄ bath of varying pH. The effect of bath solution pH and immersion time on the corrosion protection properties of SDBS:ZnSO₄ pre-treated mild steel in sodium chloride solution was investigated using electrochemical impedance spectroscopy (EIS) and polarization measurements. From the EIS results, it was found that the inhibition efficiency provided by the pre-treatment was significantly affected by the pH of the bath solution, where inhibition was highest at pH 6. This is due to the formation of a good protective layer on mild steel substrate caused by the deposition of zinc hydroxide/oxide and SDBS compound. Increasing the immersion time from 1 h to 24 h increased the inhibition efficiency. From the polarization measurements, the current density was significantly reduced, and the shift to a more positive corrosion potential value indicated a higher protection layer was formed on the metal surface during more prolonged immersion. It has been found that longer pre-treatment immersion time allows a denser protective layer formed, which prevented the diffusion of water towards the mild steel substrate that can lead to corrosion.

Abstract: In the present work, corrosion inhibition of low carbon steel in a 1M H2SO4 solution by pectin nanoparticles extract was studied by potentiostatic and weight loss methods. Increasing the acid concentration leads to an increase in the corrosion rate of the electrode. The variable conditions of the pectin nanoparticles used in this investigation are (2 to 10g/l at 25oC). It was found that the concentrates acts as a compelling consumption inhibitor for gentle steel in an acidic medium. The hindrance process is credited to the adsorbed film development of the inhibitor on the metal surface of that protects the metal against corrosion. It was observed that the efficiency of the inhibition rose with increased inhibitor concentration up to the maximum level of 92% for 10 g/l at 25 oC. The results showed that the corrosion rate without the inhibitor was 2.263mpy while with the inhibitor 0.179 mpy, meaning that the rate of corrosion improved more than 90%. The results of the immersion time (1 h) at 25oC on the inhibition of the corrosion also indicated improved corrosion resistance. The results demonstrated that an extract of pectin nanoparticles could serve as an excellent eco-friendly, green corrosion inhibitor. Fourier- transform infrared spectroscopy (FTIR) results indicate that these nanoparticles contain various chemical bonds (C-C, CH2, C-O-C, and cellulose) with metal surfaces, lead to producing a barrier layer that protects the surface.

Abstract: Corrosion is the process of natural changes in the nature of a material due to the influence or reaction with the surrounding environment. One way to control it is by adding inhibitors. In this study, seeds from guava (Psidium Guajava) were used as organic inhibitors. The test material used is API 5L grade B steel. For corrosive media, a solution of 1 M H₂SO₄ is used. In experiments used variations in the concentration of extracts 0, 2, 3, 4, 5 and 6 ml. The results of the experiments showed a decrease in the corrosion rate of API 5L grade B when there were additional inhibitors. This is supported by the experimental results of Potentiodynamic Polarization. The rate of corrosion without the presence of an inhibitor shows 75,018 mmpy whereas in the presence of 2,8845 mmpy inhibitors. Based on the calculation, the inhibition efficiency is 96.155%. This is also indicated by the results of the testing of weight loss that has been done. The efficiency shown is 90.130%.

Abstract: In order to determine the inhibitory additives concentration influence degree on the corrosion degradation rate, we studied the anode behavior of steel reinforcement made of steel grade St3 in a 10% solution NaCl with and without the inhibitors additives of various concentrations. As inhibitory additives, nitrates of potassium, sodium, magnesium, calcium and zinc were introduced into the aggressive environment, since they are often introduced into concrete compositions to accelerate their hardening. Polarization curves have been obtained for steel reinforcement in an aggressive environment, allowing the corrosion rate calculation. It was established that the introduction of potassium and zinc nitrates in an amount of 0.5% into an aggressive environment has the greatest effect on the corrosion processes’ inhibition. When nitrates of alkali and alkali-earth metals are introduced into an aggressive environment, the change in the reinforcing bars mass made of St3 steel occurs 7-8 times slower. Increasing the concentration to 1 and 1.5% is shown to be impractical, due to the small difference in the effect on the reinforcing steel anodic dissolution. A study on the effect of combining inhibitory additives on the corrosion resistance of steel reinforcement in a 10% solution NaCl was made. It was found that the combined action of inhibitors is less effective than the single effect of additives on the corrosion rate.

Abstract: A novel methodology based on electrochemical hydrogen permeation tests is proposed to study the efficiency of commercial inhibitors for industrial acid pickling of iron and mild steels. Weight loss measurements and hydrogen permeation tests have been carried out in order to compare the sensitivity of different techniques to variations of low inhibitor dosages. It has been found a close dependence between low amounts of filming inhibitors and hydrogen uptake in the metallic surface with related permeation currents. The high sensitivity of permeation currents may be very useful to establish and also control the optimum amount of active substances in industrial pickling baths, with related cost savings. The implementation of the proposed methodology to improve the control of industrial pickling plants is also envisaged, since it would be possible to improve both sensitivity and time response of experimental permeation curves.

Abstract: This article showed that new mixed inhibitor type of cucurbit [n] urils based corrosion inhibitors with gossypol at the proportion of 50:50 is excellent efficiency for mild steel in in alkaline media containing chloride ions. The Polarization Resistance results suggest that this inhibitor decreased the rate of anodic mild steel dissolution and cathodic hydrogen evolution. Increased activation energy suggested that inhibitors adsorb physically during the first step of the adsorption process.

Abstract: In reinforced concrete structures constructed on the coastline of the hypersaline Arabian Gulf water, corrosion of reinforcing steel causes cracking, delamination and spalling of concrete, within a time span of a few years. The King Abdullah Civic Center (KACC), being constructed on a reclaimed land off the coastline in the Eastern region of Saudi Arabia, is a major complex with wharves, quay walls, and breakwater and commercial buildings. To ensure the durability of buildings in the harsh marine environment and to provide a minimum service life of 35 years, a concrete mix in which 70% of Portland cement is replaced by granulated ground blast furnace slag (GGBFS) was recommended based on durability modeling conducted using the software STADIUM^®. Concrete with 70% GGBFS provides for the dual objective of achieving a green concrete and an enhanced service life of the building. Based on durability modelling it was concluded that corrosion inhibitor should be used preferably in the concrete. A detailed experimental program was conducted to assess the durability and strength properties of the 70% GGBFS concrete, with and without corrosion inhibitor. This paper presents the results of experimental investigations and durability modeling conducted for the project. A 70% GGBFS concrete mix without corrosion inhibitor was adopted for the raft foundation and subsequently for the entire building to make it a green concrete building.

Abstract: In Petrobrás SA refineries, there are thousands of heat exchangers in which cooling water is treated for recycling, often by outsourced companies. In all of these refineries there happens shutdown for corrective maintenance of the exchangers by problems related to corrosion caused by the cooling water, requiring about four days to repair a unit. The shutdown of a production line results in loss of revenue between U$ 200,000.00 and U$ 300,000.00 per day. To control the cooling water quality, it is used coupons for corrosion analysis. Tests are limited to visual inspection and by mass loss analysis. In this work, inhibitors such as sodium nitrite, sodium dichromate and benzoic acid are used to protect metals immersed in water in order to avoid the corrosion and consequently the shutdown of the exchanger for corrective maintenance.