Experimental Technology and Management

[Objective] Multiphase erosion-corrosion in pipelines and elbows is caused by the combined action of particle impact， fluid shear， electrochemical corrosion， and their interaction. Existing rotary， jet-type， and conventional pipe-flow devices are limited in reproducing actual pipe-flow conditions， visualizing local flow behavior， comparing damage at different elbow positions， and obtaining mass-loss and electrochemical information under the same operating condition. Therefore， a pipe-flow multiphase erosion-corrosion experimental platform was designed to generate solid-liquid， gas-liquid， and gas-liquid-solid flow conditions， observe multiphase flow in a transparent elbow， characterize local damage， and quantitatively distinguish mechanical erosion， electrochemical corrosion， and their synergistic contribution. [Methods] The platform consisted of a material circulation system， a gas supply system， a transparent observation section， a 90° transparent elbow test section， a specimen installation unit， a mass-loss measurement module， a three-electrode electrochemical monitoring system， and a control and data acquisition system. Metal specimens were installed at the 0°， 45°， and 90° positions of the elbow. The specimens were embedded in epoxy resin， with the exposed metal surface flush with the inner wall. Blank epoxy specimens were tested simultaneously to correct the mass loss of the resin-covered area. A 20 steel specimen， a saturated calomel electrode， and a platinum electrode were used as the working， reference， and counter electrodes， respectively. Open-circuit potential and potentiodynamic polarization curves were collected during operation， and mass loss was measured after cleaning， drying， and weighing the specimens. The platform was evaluated in terms of flow regulation accuracy， 8 h operating stability， repeatability， spatial resolution， and consistency between mass-loss and electrochemical results. Coal-water slurry and 20 steel were selected as the representative solid-liquid system. Flow velocities of 1.0–2.6 m/s and particle mass fractions of 5%–25% were investigated. Comparative slurry experiments and electrochemical measurements were further combined to separate total damage into mechanical erosion， electrochemical corrosion， and synergistic contributions. [Results] The platform successfully generated solid-liquid， gas-liquid， and gas-liquid-solid flow conditions. Within the adjustable velocity range of 0.5–3.0 m/s， the deviation between the measured and preset velocities was less than ±0.1 m/s. During continuous operation for 8 h， the flow fluctuation was less than ±3.5%， and the relative standard deviation of repeated experiments was below 7%. Under the same operating condition， the specimen at the 90° elbow position showed the greatest mass loss， followed by those at the 45° and 0° positions. The variation trends obtained from polarization curves were consistent with the mass-loss results. When the slurry velocity increased from 1.0 to 2.6 m/s， the erosion-corrosion rate at the 90° position increased from 2.16 to 4.12 mm/a. With increasing velocity， surface damage changed from scattered impact pits and shallow scratches to deeper grooves， impact craters， and local spalling. Increasing particle concentration generally increased the erosion-corrosion rate， but the increase gradually weakened at high concentrations because of intensified particle-particle collisions and shielding effects. The contribution of mechanical erosion increased from 22.69% to 53.25%， whereas the synergistic contribution decreased from 51.38% to 9.16% as the velocity increased from 1.0 to 2.6 m/s. [Conclusions] The developed platform integrates multiphase-flow generation， transparent visualization， multi-position specimen testing， mass-loss analysis， and electrochemical monitoring. It provides reliable flow control， stable long-duration operation， satisfactory repeatability， and sufficient spatial resolution. The platform can characterize the effects of flow velocity and particle concentration and quantitatively distinguish the contributions of mechanical erosion， electrochemical corrosion， and their synergistic interaction. It can be used for multiphase erosion-corrosion mechanism research， process equipment protection studies， experimental teaching， and student research training.