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Equipment and typical results from cathodic protection surveying systems. In the simplest form, cathodic protection surveying of fixed offshore platforms is achieved by the so called ‘dipping’ technique, dipping a reference electrode into the sea and measuring a steel/sea potential with respect to it via an indicating voltmeter and a metallic connection to the topside steelwork. This procedure is allowed in NACE RP‐01–76 REF 36 but the standard does address the importance of placing the electrode close to platform members, distant from anodes and into areas of greatest shielding. The conventionally undertaken dip survey, particularly in geographic regions with substantial sea currents which cany the electrode away from structure members, is nothing better than a general indication of the overall level of protection. The probability is of errors indicating better levels than actually exist, due to the IR related voltage drops in the sea between the electrode location and the platform member.

The purpose of this paper is to study the corrosion process by examining the deterioration of X80 steel exposed to a real petroleum sample containing condensed hydrocarbon plus oilfield-produced water, which were subjected to stimulated emulsions in flowing media at 50°C.

The impedance and polarization spectra were used to assess the aggressiveness of the petroleum sample and tried to find a washing process using condensed hydrocarbon with deionized water. Mössbauer technique was used to identify the phases in precipitated ions obtained during an oven-drying procedure of the oilfield produced water.

The emulsion, chloride, sulphur compounds, heavy metals and the use of a double hydrodynamic system were the most important factors affecting the corrosion of X80 steel. The corrosion rate of this steel increased when oilfield-produced water was stimulated by a double hydrodynamic system (4.56 mm/year). It was determined to be 7.66 mm/year and 4.01 mm/year when steel was exposed to a stimulated emulsion using the petroleum sample and condensed hydrocarbon with deionized water at 24 h, respectively, suggesting that a significant process of hydrocarbon washing could occur and a more corrosive solution was highlighted. Mössbauer results showed that the ions precipitates included the following phases at Wt.%: magnetite (20.0), greigeite (22.8), siderite (3.2), pyrite (2.9), marcasite (26.7) and mackinawite (24.4).

A stimulated hydrocarbon/water emulsions with a more homogeneous solution containing high concentrations of saline compounds and heavy metals were used to simulate the susceptibility to corrosion on the internal pipeline steels exposed to any type of immiscible liquids such as condensed hydrocarbon, or crude oil, containing water. A practical application of the presented research could provide a novel framework for understanding the internal corrosion in pipelines from the simulation of washed hydrocarbons after the stimulated emulsions that can be found in the field. Because more susceptibility to corrosion for pipeline steels would be expected at the end of the transportation of the fluid. It is possible to investigate the possible corrosion mechanisms by using a dried oilfield-produced water sample interacting with the pipeline steels.

The purpose of this paper is to study the corrosion rate for X52, X60, X65, X70 and X80 steel immersed in Mexican oilfield produced water. For the electrochemical characterization of the five steels rotating disk electrodes, 20°C, 30°C and 45°C of experimental temperature and 0, 500, 1,000 and 2,000 rpm of rotation speed were taken into account. The temperature dependence was analyzed using Arrhenius law. Thus, Rct values obtained from EIS data in comparison with the corrosion rate obtained from polarization curves data were taken into account. Hydrodynamic effects were analyzed by Rct and corrosion rate data.

Electrochemical impedance spectroscopy and potentiodynamic polarization techniques were used to assess the electrochemical behavior for five pipe steels steel immersed in a natural solution.

The resistance and corrosion rate taken from electrochemical tests decreased as temperature and hydrodynamic condition also decreased. In addition, the Arrhenius parameter revealed that the natural solution increased the corrosion rate as the activation energy decreased. Typical branches related to reduction-oxidation reaction (dissolution-activation process or corrosion products dissolution) on steel surface were discussed. Optical images analysis shows that corrosion products for X65 steel exposed to oilfield produced water can be attributed to more susceptibility to corrosion damage for this steel grade (Quej-Ake et al., 2018), which is increased with the temperature and rotation speed of the working electrode.

Corrosion process of the five steels exposed to oilfield produced water could be perceptive when Arrhenius analysis is taken into account. This is because oilfield produced water is the most aggressive condition (brine reservoir and sour water) for internal pipelines walls and storage tanks (brine tanks). Thus, stagnant condition was considered as a more extreme corrosive condition because produced water is stored in atmospheric stationary tanks as well as it is transported under laminar condition in zones where oilfield produced water is maintaining in the bottom of the pipe during the production, transporting and storing of the crude oil. In addition, a brief operational process for Reynolds number and the flowrate of the stock tank barrel per day (Q in STBD) using field and Reynolds number data is discussed.

Bimetallic composite pipe consists of a corrosion resistance alloy (CRA) layer for corrosion resistance and carbon steel for mechanical properties, which shows a promising prospect of gathering pipeline with its effective-cost and reliable corrosion resistance. However, the corrosion resistance of composite pipe is determined by the quality of its welding gap. This paper aims to investigate the TIG welding gap corrosion resistance of X52/825 metallurgical clad pipe in H₂S/CO₂ environment.

Corrosion tests of X52/825 welding gap were performed in a stimulated gas field solution containing both 1 MPa CO₂ and 1.5 MPa H₂S at 70°C for 720 h in a self-designed high temperature and high pressure autoclave. The anti-stress corrosion cracking (SCC) performance of X52/825 clad pipe ring root welding gap was investigated in both NACE A solution and the stimulant gas field solution by four point bending testing and constant load test. Then the experiments were rerun in XX high sour gas well. In addition, the alloy diffusion and microstructure characteristics of TIG welding gap were analyzed through scanning electron microscopy and energy dispersive X-ray spectroscopy technologies.

The results reveal that the root welding gap is almost not corroded in the stimulant gas field solution, and no micro-cracks were observed by electron microscope. Anti-SCC test results show the root welding gap does not break, indicating a good resistance to environmental-cracking in H₂S/CO₂ environment. The transition layer can be obviously observed in the root welding zone, and the alloy content of transition layer is diluted. However, the transition layer does not penetrate into the inner of CRA layer, which illustrates its good anti-corrosion performance. Therefore, TIG welding technology can be well used in the welding process of composite pipe.

This paper may provide theoretical reference for manufacturing and application of clad pipe.