Painting over soluble salts: Field extraction of soluble salts from corrosion products of steel

摘要

When soluble salts are present at the steel/organic coating interface, premature deterioration of the coating is often observed. Therefore, for a steel structure to be adequately protected by means of a paint coating, it is convenient to previously know the nature and the concentration of the soluble salts that are present at the interface. There is a constant demand on the part of industry and organisations, such as International Standard Organisation (ISO) and Steel Structures Painting Council (SSPC), etc., for improved methods for field extraction and analysis of soluble salts. Innovations in this respect are focused on the development of extraction cells that achieve higher soluble salt extraction efficiency-especially, when the surface is covered by rust or oxide layers that hinder their extraction-greater specificity in the analysis of the different ions and increased versatility, so that the extraction cell can be adapted to the different geometric configurations that may arise in the steel structures in practice. This paper assesses the extraction efficiency of a new field extraction method that allows the nature and the concentration of soluble salts present on the steel surface to be known with greater precision. The results of a comparative study with other commercial extraction cells, performed on rusted steel surfaces obtained both by natural exposure in the atmosphere and artificially in climate cabinets, show that the new extraction method positively affect the soluble salt extraction efficiency.