Effect of SAW fluxes on electrochemical corrosion & microstructural behavior of API X70 weldments

High-performance pipeline steels are frequently used for storage, transportation and energy development applications. Submerged arc welding finds its application to weld thick pipes. Design and development of appropriate welding fluxes provide good structural integrity properties in severe service environments. The present study aims to investigate the effect of laboratory-developed SAW fluxes on the electrochemical corrosion behavior of SAW weldments in different environments. Electrochemical corrosion behavior of weld specimens in different environments was performed using Linear Sweep Voltammetry. Different mediums such as seawater and sodium thiosulphate solution (10−2 Mol/l, pH = 3, and 10−3 Mol/l, pH = 5) were taken for the corrosion study. The microstructure of the weld specimen reveals the presence of acicular ferrite structure. F3RA and F19RA weld specimen shows a higher corrosion rate in seawater and sodium thiosulphate medium (pH = 3 or 5).

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Corrosion Resistances of As-Cast and Quenched Samples of a Zn-22Al Eutectoid Alloy

Materials Science Forum ◽

10.4028/www.scientific.net/msf.587-588.355 ◽

2008 ◽

Vol 587-588 ◽

pp. 355-359 ◽

Cited By ~ 1

Author(s):

Wislei R.R. Osório ◽

Noé Cheung ◽

Leonardo R. Garcia ◽

Amauri Garcia

Keyword(s):

Heat Treatment ◽

Corrosion Behavior ◽

High Performance ◽

Electrochemical Impedance ◽

Cast Alloy ◽

Electrochemical Corrosion ◽

Alloy Sample ◽

Mechanical And Tribological Properties ◽

Electrochemical Corrosion Behavior ◽

Eutectoid Alloy

To address the increasing demand for high performance and high quality die castings, Zn-Al casting alloys have been developed, in particular for applications in the automotive industry. This family of alloys has good physical, mechanical and tribological properties and is commonly used as foundry alloys in a variety of applications. Particularly, the Zn-22 wt% Al eutectoid alloy is a classic commercial material and a fine-grained structure can be obtained by using a suitable heat treatment which can induce a superplastic behavior. On the other hand, this heat treatment can affect the corrosion behavior of such alloy. The present work focuses on the influence of as-cast and quenched microstructures of the Zn-22wt%Al eutectoid alloy on its electrochemical corrosion behavior. The typical microstructural patterns were examined by using optical microscopy techniques. In order to evaluate the corrosion behavior of such alloy, corrosion tests were performed in a 0.5 M NaCl solution at 25°C by using an electrochemical impedance spectroscopy (EIS) technique and potentiodynamic polarization curves. An equivalent circuit by using the ZView software was also used to provide quantitative support for the discussions and understanding of the electrochemical corrosion behavior. It was found that the heat-treated samples are more susceptible to the corrosion action than the as-cast alloy sample.

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