Yuli Panca Asmara

Efficient design of response surface experiment for corrosion prediction in CO2 environments

Abstract Carbon dioxide corrosion involves several factors that complicate corrosion mechanisms due to the possible interactions (synergies, etc.) among the species present. Selective study of each individual effect, by either empirical or mechanistic modelling, is unlikely to uncover these interaction effects satisfactorily. This paper demonstrates the use of response surface methodology as a method to optimise experiments so as to capture better synergies between species and conditions. Here, the multiple effects of acetic acid, temperature, flowrate and pH are studied in the model, which was validated by experiment, prediction software and published corrosion data. In conclusion, the proposed model has shown a good agreement with the validation data, which indicates the suitability of the approach used to model carbon dioxide corrosion at pH 4–5·5.

Predicting Effects of Corrosion Erosion of High Strength Steel Pipelines Elbow on CO2-Acetic Acid (HAc) Solution

Simultaneously effect of erosion combined with corrosion becomes the most concern in oil and gas industries. It is due to the fast deterioration of metal as effects of solid particles mixed with corrosive environment. There are many corrosion software to investigate possible degradation mechanisms developed by researchers. They are using many combination factors of chemical reactions and physical process. However effects of CO2 and acid on pipelines orientations are still remain uncovered in their simulation. This research will investigate combination effects of CO2 and HAc on corrosion and erosion artificial environmental containing sands particles in 45°, 90° and 180° elbow pipelines. The research used theoretical calculations combined with experiments for verification. The main concerns are to investigate the maximum erosion corrosion rate and maximum shear stress at the surface. Methodology used to calculate corrosion rate are Linear Polarization Resistance (LPR) and weight loss. The results showed that at 45°, erosion rate is the more significant effects in contributing degradation of the metal. The effects of CO2 and HAc gave significant effects when flow rate of the solution are high which reflect synergism effects of solid particles and those chemical compositions.

Flow Assisted Erosion-Corrosion of High Speed Steel (HSS) in Nanofluid Coolant

The use of nanocoolant is suspected to have effects on erosion-corrosion of piping systems in heat exchanger. This study was carried out to determine the erosion corrosion of AISI 316 stainless steel in solutions containing nanoparticles. The experiments used rotating cylinder electrode (RCE) at rotational speed of 0-1800 rpm under varying temperature of 30oC-70oC. Corrosion rate was measured using linear polarization resistance (LPR) method and erosion was indicated by measuring average depth of surface of the samples (surface roughness). The results showed that both corrosion rate and surface roughness of samples have increased when temperature and rotation speed increased. The erosion-corrosion effects of nanocoolant were lower in stagnant condition. Comparing with conventional coolant, the nanofluid showed significant differences. In flow conditions, the effects were remarkable. It was also found that maximum synergism erosion and corrosion were occurred at higher temperature and high rotation speed for both of types solutions.

High temperature oxidation in boiler environment of chromized steel

The demand for increasing efficiency has led to the development and construction of higher operating temperature power plant. This condition may lead to more severe thickness losses in boiler tubes due to excessive corrosion process. Hence, the research to improve the corrosion resistance of the current operated material is needed so that it can be applied for higher temperature application. In this research, the effect of chromizing process on the oxidation behaviour of T91 steel was investigated under steam condition. In order to deposit chromium, mixture of chromium (Cr) powder as master alloy, halide salt (NH4Cl) powder as activator and alumina (Al2O3) powder as inert filler were inserted into alumina retort together with the steel sample and heated inside furnace at 1050°C for ten hours under argon gas environment. Furthermore, for the oxidation process, steels were exposed at 700°C at different oxidation time (6h-24h) under steam condition. From FESEM/EDX analysis, it was found that oxidation rate of pack cemented steel was lower than the un-packed steel. These results show that Cr from chromizing process was able to become reservoir for the formation of Cr2O3 in high temperature steam oxidation, and its existence can be used for a longer oxidation time.

Long Term Corrosion Experiment of Steel Rebar in Fly Ash-Based Geopolymer Concrete in NaCl Solution

This research focuses on an experimental investigation to identify the effects of fly ash on the electrochemical process of concrete during the curing time. A rebar was analysed using potentiostat to measure the rest potential, polarization diagram, and corrosion rate. Water-to-cement ratio and amount of fly ash were varied. After being cured for 24 hours at a temperature of 65°C, the samples were immersed in 3.5% of NaCl solution for 365 days for electrochemical measurement. Measurements of the half-cell potential and corrosion current density indicated that the fly ash has significant effects on corrosion behaviour of concrete. Although fly ash tends to create passivity on anodic current, it increases corrosion rate. The corrosion potential of this concrete mixture decreases compared to concrete without fly ash. From the result, it can be summarized that concrete mixture with 70% of OPC (Ordinary Portland Cement) and 30% fly ash has shown the best corrosion resistance.

Improving Efficiency of Aluminium Sacrificial Anode Using Cold Work Process

Aluminium is one of the preferred materials to be used as sacrificial anode for carbon steel protection. The efficiency of these can be low due to the formation of oxide layer which passivate the anodes. Currently, to improve its efficiency, there are efforts using a new technique called surface modifications. The objective of this research is to study corrosion mechanism of aluminium sacrificial anode which has been processed by cold work. The cold works are applied by reducing the thickness of aluminium sacrificial anodes at 20% and 40% of thickness reduction. The cathodic protection experiments were performed by immersion of aluminium connected to carbon steel cylinder in 3% NaCl solutions. Visual inspections using SEM had been conducted during the experiments and corrosion rate data were taken in every week for 8 weeks of immersion time. Corrosion rate data were measured using weight loss and linear polarization technique (LPR). From the results, it is observed that cold worked aluminium sacrificial anode have a better corrosion performance. It shows higher corrosion rate and lower corrosion potential. The anodes also provided a long functional for sacrificial anode before it stop working. From SEM investigation, it is shown that cold works have changed the microstructure of anodes which is suspected in increasing corrosion rate and cause de-passivate of the surface anodes.

Electrochemical Behaviour of High Stress Steel (AISI 4340) in CO2 Environments with the Presence of H2 Gas

This research studied the effect of CO2 and H2 gas on electrochemical behaviour of high stress steel (HSS) by using scan polarization graph to measure corrosion rate, corrosion potential and pitting potential. The tensile test samples with and without notches were tested under constant stress of 20% and immersed in 3% NaCl solutions. During experiments, CO2 gas was injected into the samples. To generate H2 gas, the samples were employed cathodically over potential at - 1700 mV (Ag/AgCl) for three days. The results indicated that both CO2 and H2 gases have increased the corrosion rate. Potentiodynamic graph showed that there were changes in pitting potential where the effect of CO2 gas would decrease the pitting potential. However, the presence of the notch did not show any significant difference in corrosion rate.

Influences of H2SO4 and NaCl Concentrations on Stress Corrosion Cracking of AISI 304 Stainless Steel

This paper presents the influence of H2SO4 and NaCl concentrations on the corrosion mode of AISI 304 stainless steel in H2SO4-NaCl aqueous solutions. Immersion test was conducted at room temperature using U-bend specimens. The specimens in annealed and sensitized conditions were immersed in aqueous solutions containing H2SO4 concentration in the range of 0 to 3.0 kmol/m3 with 1.5 kmol/m3 interval, and NaCl concentration in the range of 0.5 to 2.0 kmol/m3 with 0.5 kmol/m3 interval. Results showed that, specimens in sensitized condition have a higher mass loss and higher corrosion rate. In addition, the experimental result also indicates that the two solutes have synergistic effect on corrosion mode of the material that is stress corrosion cracking (SCC) and general corrosion, which occur within a specific range of concentration. SCC region became smaller as the H2SO4 and NaCl concentration increased. However, the occurrence of SCC was high when sensitization treatment was subjected to the specimens. The appearance of surface damage and crack morphology were revealed by using scanning electron microscopy (SEM).

Mechanistic model of stress corrosion cracking (scc) of carbon steel in acidic solution with the presence of H2s

In oil and gas industrial environments, H2S gas is one of the corrosive species which should be a main concern in designing infrastructure made of carbon steel. Combination between the corrosive environment and stress condition will cause degradation of carbon steel increase unpredictably due to their simultaneous effects. This paper will design a model that involves electrochemical and mechanical theories to study crack growth rate under presence of H2S gas. Combination crack and corrosion propagation of carbon steel, with different hydrogen concentration has been investigated. The results indicated that high concentration of hydrogen ions showed a higher crack propagation rate. The comparison between corrosion prediction models and corrosion model developed by researchers used to verify the model accuracy showed a good agreement.