International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

Galvanized steel pipes have long been widely used in drinking water supply systems due to the zinc coating that protects the steel from corrosion. However, during operation, especially when hot water is supplied, the zinc protective layer gradually breaks down, especially if there are galvanic pores in the pipeline or stray electric currents are generated in the pipeline. If the zinc coating is damaged, the steel base begins to corrode, rust forms, the pipe wall thickness decreases and the water quality deteriorate.
In addition to internal corrosion, a significant problem is external pipe corrosion caused by condensation forming on the surface of cold-water pipes. When the pipe surface temperature is below the dew point of the ambient air, moisture accumulates on it. Long-term wetting of the surface, especially if the zinc coating or protective paint layer is damaged, creates favorable conditions for the development of atmospheric corrosion. The corrosion process is further accelerated by poor indoor ventilation, high relative humidity or incorrectly calculated insulation layer thickness.
The article will examine two corrosion situations of steel pipes for drinking water supply using metallographic, water parameter studies, and stray current measurements.

High-frequency electric resistance welding is one of the most common process for production of longitudinal seam welded carbon steel pipes suitable for line pipe, casing and tubing. In this pipe production process, the hot rolled strip goes into the forming mill where it is gradually cold formed into a tubular shape in several stages of forming rolls and its edges are continuously joined by a combination of localized electrical resistance heating and forge pressure. High frequency electric resistance welding generally involves high temperature, forge pressure and subsequent cooling, and as the result of this thermal cycle occurs significant microstructural changes. These microstructural changes provides a wealth of information on weld seam quality and edge preparation of hot rolled strips.

In this paper, microstructural changes in the forge weld area during high frequency electric resistance welding (HFERW) of longitudinal seam welded pipes Ø114.3×5.21mm were investigated.