Scale formation mechanism and green strategies for its prevention and control

Scale formation is a common operational problem in aqueous, industrial and oilfield systems where dissolved mineral ions exceed their solubility limits and precipitate as solid deposits. This manuscript reviews the mechanisms of scale formation, the factors influencing deposition, the major types of scale, and the approaches used for scale prevention, inhibition and removal. Scale development generally occurs through supersaturation, nucleation, crystal growth, surface deposition and ageing. Its formation is influenced by water hardness, temperature, pressure, pH, ionic strength, CO₂ partial pressure, fluid velocity and surface roughness. The manuscript discusses several scale types, including calcium oxalate, calcium carbonate, calcium sulfate, calcium sulfite, calcium phosphate, calcium aconitate, calcium citrate, silicate scale and sugar-charcoal deposits. These deposits may reduce heat-transfer efficiency, restrict fluid movement, increase energy consumption, damage equipment and contribute to operational downtime. Prevention and inhibition strategies include chemical inhibitors, mechanical techniques, operational adjustments and green inhibitors derived from natural or biodegradable sources. Conventional inhibitors remain useful; however, environmental concerns have encouraged interest in plant extracts, natural polymers and other eco-friendly alternatives. The review also notes that green inhibitors may present practical challenges, including removal from systems after application. Overall, the manuscript emphasises the need to connect scale-formation mechanisms with safer and more effective inhibition strategies.