Protection of internal weld using a silicate coating

Abstract

The main disadvantage of steel pipes and pipeline parts is their sensitivity to corrosion, which leads to a huge waste of metal and reduces the pipeline service life. In the past 15 years, the oil and gas industry has seen a drastic increase in the production of internally coated pipes and pipes made from corrosion-resistant materials. Therefore, their connection must have the same strength, pressure tightness and corrosion resistance as the material of a main pipe. The need to protect the weld is due to the weld and the connected area is the most vulnerable point in the structure. Therefore, the purpose of this work is to develop a technology for enameling the steel pipeline weld with an internal vitreous silicate enamel coating. The components were weighed, mixed and melted. The resulting frit is an X-ray amorphous glass phase. On the basis of the obtained frit, enamel slurries of the required fineness and composition were prepared and tested for the main rheological properties: density; covering ability (amount of slurry retained on a metal product surface); fineness of grinding (degree of frit grinding in slurry suspension); sedimentation stability (resistance of system particles to settling). Slurry was applied to the pretreated steel samples by pouring method. Then the samples were dried for 7-10 minutes at a temperature of 70-90 °C. Fastening firing was carried out in an electric furnace in the temperature range of 750-950 °C for 5 minutes. The quality of the weld and the presence of defects were analyzed after cooling. The optimal composition was chosen. It is characterized by the following advantages: complete melting of the enamel; absence of “copper heads”; absence of bubble craters, as well as small bubbles in the enamel volume; absence of burnouts. Further, the main technical and operational properties of the protective coating for the pipe weld were investigated: chemical resistance to the acid and alkali solutions; “coating – metal” adhesion strength; wear resistance (abrasion resistance). The results obtained demonstrate high protection rates of the synthesized coating, its high durability and reliability. The work was supported by the Russian Science Foundation, Project # 18-19-00455 “Development of integrated protection technology for oil and gas pipelines, operated in the Far East of Russia” in the framework of the 2018 competition “Conducting fundamental scientific research and exploratory scientific research by individual scientific groups”.