Influence of Calcium Scaling on Corrosion Behavior of Steel and Aluminum Alloys

Electrochemical Study on the Macro-Cell Corrosion of Pipeline Steel Partially Covered by Different Kinds of Mineral Deposits

This study presents the impact of mineral deposits (SiO2, Al2O3, and CaCO3) on the corrosion behavior of X65 pipeline steel in CO2-containing brine solution with low pH. The study investigates the initiation and propagation of under deposit corrosion (UDC) using a wire beam electrode (WBE) partially covered by different mineral deposit layers, in conjunction with electrochemical measurements and surface characterization. The results indicate that the corrosion behavior varies, depending on the characteristics of the deposit. During the test period, the Al2O3-covered steel acted as the main anode with more negative potential, while the bare steel acted as the cathode. The SiO2-covered steel acted as the cathode with more positive potential and a localized FeCO3 layer formed beneath the silica mineral. The CaCO3-covered steel initially acted as an anode with a more negative potential but transformed into the cathode at the end of the test. Additionally, shallow and small pits were observed beneath the deposits with the depth in the sequence Al2O3 > SiO2 > CaCO3.

Formation mechanisms and supervisory prediction of scaling in water supply pipelines: A review

The scaling problem in the water supply pipeline will increase the resistance coefficient of the pipeline and the pressure of the water supply pipeline, which will not only affect the operation safety of the water supply pipeline, but also cause energy waste. The scale in the pipeline will also enrich heavy metal ions and pathogenic microorganisms, affecting the safety of water supply water quality and causing secondary pollution of water quality. At present, a lot of research has been done on the composition structure and crystallization process of the scale. The study found that calcite is the main component of the scale; the scale process is a heterogeneous nucleation process induced by heavy metal particles and their corrosion products in the pipeline. The introduction of electrochemical detection technology, density functional theory and molecular dynamics simulation has greatly improved the accuracy and timeliness of water scaling conditions detection and realized the visualization of scaling mechanism. In this paper, the measurement methods of the scale in the water supply pipeline and the corresponding material composition and crystal structure characteristics are reviewed, and the mechanism of the scale and the water quality conditions are summarized. At the end of this paper, based on summarizing the existing water quality scaling tendency evaluation methods, it is proposed to establish a water quality potential scaling risk assessment framework based on Puckorius scaling index (PSI) and electrochemical impedance spectroscopy (EIS) in the future.

Sulfate mineral scaling: From fundamental mechanisms to control strategies

Sulfate scaling, as insoluble inorganic sulfate deposits, can cause serious operational problems in various industries, such as blockage of membrane pores and subsurface media and impairment of equipment functionality. There is limited article to bridge sulfate formation mechanisms with field scaling control practice. This article reviews the molecular-level interfacial reactions and thermodynamic basis controlling homogeneous and heterogeneous sulfate mineral nucleation and growth through classical and non-classical pathways. Common sulfate scaling control strategies were also reviewed, including pretreatment, chemical inhibition and surface modification. Furthermore, efforts were made to link the fundamental theories with industrial scale control practices. Effects of common inhibitors on different steps of sulfate formation pathways (i.e., ion pair and cluster formation, nucleation, and growth) were thoroughly discussed. Surface modifications to industrial facilities and membrane units were clarified as controlling either the deposition of homogeneous precipitates or the heterogeneous nucleation. Future research directions in terms of optimizing sulfate chemical inhibitor design and improving surface modifications are also discussed. This article aims to keep the readers abreast of the latest development in mechanistic understanding and control strategies of sulfate scale formation and to bridge knowledge developed in interfacial chemistry with engineering practice.

Evaluation of corrosion and scaling potentials of oilfield waters in an offshore producing facility, Niger Delta

In this study, water samples from Miocene reservoirs, offshore Niger Delta, and seawater samples used for water injection were investigated in an attempt to examine the chemistry, evaluate the corrosion behaviour of steel, iron, and aluminium in different aqua media, and evaluate the scaling potentials of the oilfield produced waters (OFPW). Chemical analyses of the waters were determined; corrosion rate measurements were carried out by the weight loss method at room temperature while corrosion kinetics was carried out using conventional methods. Langelier saturation index (LSI), Ryznar stability index (RSI), Larson-Skold index (L-S), Puckorius scaling index (PSI), and aggressiveness index (AI) were evaluated for assessing the corrosiveness and scaling potential of the formation waters, using water quality data. The magnitude of corrosion of these metals was studied for an exposure period of 42 days. Chemical analysis revealed that the waters are slightly alkaline and generally classified as hard, saline water of the Na-Cl type based on its total dissolved solids (TDS). Produced water pH values range from 7.32 to 8.38. Results showed the likelihood of some of the water to form mild to severe scales based on the corrosivity indices, while the seawater samples are classified as 'non-aggressive' and 'aggressive'. Steel has the highest corrosion rate with a value of 3.84 × 10^-3 mg cm^-2 h^-1 compared to aluminium with the lowest rate of 0.37 × 10^-3 mg cm^-2 h^-1. In most cases, the rate of corrosion of the metals followed the first-order rate constant in some of the samples, and the second-order in others within the first seven days. It was observed that the rate of corrosion follows this order: steel > iron > aluminium. The potential heavy and intolerable corrosion associated with the use of these seawater samples as injection waters is a potential risk that must be handled by adequate treatment.