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This study addresses the challenge of preferential weld corrosion in ASTM A333 carbon steel piping, investigating the intricate interplay of various factors. The welding process induces microstructural alterations, making affected areas more prone to corrosion, resulting in Preferential Weld Corrosion (PWC). While the addition of 1 % nickel filler shifts the galvanic potential of Weld Metal (WM), its impact on PWC is marginal due to the high rates of its intrinsic corrosion. Notably, nickel filler addition accelerates corrosion in the heat-affected zone (HAZ). In carbon dioxide (CO2) environments, the presence of acetic acid (HAc) intensifies corrosion; yet, the application of morpholine as pH neutralizer effectively counters its effects. Imidazoline based corrosion inhibitor prove successful in PWC mitigation, particularly at elevated pH levels. Furthermore, Post Weld Heat Treatment (PWHT) significantly reduces hardness, aligning with a decrease in corrosion. Of paramount importance, this study not only examining the effects of individual factors, including microstructure, pH adjustment, corrosion inhibitors, and PWHT, but also scrutinizing their combined impacts. The integration of PWHT with pH adjustment and inhibitor injection yields corrosion rates below 0.1 mm/y, ensuring a remarkable 30-year service life even under challenging conditions. This study underscores the necessity of a comprehensive strategy, combining these factors, to effectively manage preferential weld corrosion in carbon steel weldments.

In recent years, there has been an increasing interest in open-hole and filled-hole laminate failure analysis. The open and filled-hole laminate failure analysis is used in several important areas, especially in designing mechanically fastened composite joints. Various analytical, empirical, and numerical methods are available for the design of mechanically fastened composite joints. The large number of material and geometrical design variables at the preliminary design stage makes the empirical and numerical methods effortful, expensive, and time-consuming. Therefore, analytical methods are recommended over numerical and empirical methods at the preliminary design stage merely because of their simplification in calculations, making them computationally efficient. Taking this into consideration, current research presents an improvement to the analysis capabilities of the previously introduced analytical method, i.e., the coupled approach of Classical laminate theory (CLT) and Lekhnitskii solutions. These improvements include the development of failure envelops for the open-hole and filled-hole laminates, estimation of optimized filling material for attaining maximum load-bearing capacity of filled-hole laminates, and optimization of stacking sequence for maximum load-bearing capacity of open-hole and filled-hole laminates. From the failure envelop results, it was found that failure envelopes of filled-hole laminates are bigger than open-hole laminates. Furthermore, it was found that the stiffness of the filling material should be equal to the stiffness of the laminate to achieve maximum bearing strength of the filled-hole laminate. It was also demonstrated that the coupled approach of CLT and Lekhnitskii solutions may provide carpet plots that can be utilized to optimize the stacking sequence for open-hole and filled-hole laminates.

Chloride-Induced Stress Corrosion Cracking (CISCC) has been frequently reported in the petrochemical industries where it usually causes failure to the austenitic stainless steel structures encased with thermal insulation in a chloride-containing environment. This study aims to analyze and evaluate the risk of chloride concentration and different types of insulation materials on CISCC of Austenitic SUS 304L. The experimental study was carried out for 14 days using U-bend specimens through the Drip Test apparatus, as per ASTM G30 and ASTM C692. U-Bend specimens were installed onto the test rig and shielded with different insulation materials. Sodium chloride (NaCl) salt solutions were periodically dripped onto the specimens, to simulate the wet and dry cycle. Insulation materials used were rockwool, calcium silicate and perlite, whereas the concentrations of NaCl solutions were set at 0.1, 1.0 and 3.5 wt.%. The specimens were inspected using dye penetration tests (DPT), stereo microscope and optical microscope throughout the study to determine the CISCC susceptibility. Results showed that cracking was observed on the specimen with rockwool insulation at 3.5 wt% NaCl and 90°C. Rockwool has a high water absorption capacity at which saltwater will evaporate when in contact with a hot metal surface, resulting in the build-up of salt deposits of high concentration over time. SCC was not observed on other specimens with different conditions, but salt deposits, general corrosion and pitting corrosion were found. From the study, the thermal insulation of rockwool was found to have the highest tendency to cause SCC, followed by calcium silicate and perlite.

Errors in the measurements of pipeline nondestructive tools may lead to faulty decisions causing economic and environmental loss, or system failures. Calibration models are an effective tool that is used to enhance the quality of corrosion measurements affected by inline inspection tools sizing accuracy. Parametric calibration models are limited to datasets with Gaussian behavior. On the other hand, non-parametric calibration models can overcome the normality limitation, however, they provide only a local or general estimation. This paper presents a new hybrid calibration model that is based on two steps K nearest neighbor interpolation and support vector regression. The suggested hybrid model uses both general and local estimation behaviors for the calibration process, hence resulting in a better prediction. The hybrid algorithm was evaluated using a dataset of pipeline corrosion measurements collected by a Magnetic Flux Leakage (MFL) sensor (with an error margin of ±20% of the true values), and an Ultrasonic (UT) device (with an error margin of ±4%). The suggested approach resulted in reducing the errors in MFL corrosion measurements to be only ±6.82% instead of the original ±20%.

Wall shear stress produced by turbulent multiphase flow is considered an important parameter in CO 2 corrosion as it has been claimed to be responsible for the removal of protective corrosion product layers and corrosion inhibitor films. In this study, a floating element wall probe was used to directly measure wall shear stress in multiphase flow; the highest measured values were of the order of 100 Pa. Findings suggest that the wall shear stress alone, produced in multiphase flow patterns covered in the present study, is insufficient to mechanically damage the protective corrosion product layers or corrosion inhibitor films. [ABSTRACT FROM AUTHOR]