INVESTIGATION CORROSION BEHAVIOUR OF DUCTILE CAST IRON WELD JOINT IN SEA WATER

الملخص

Manual metal-arc welding was carried out for ductile cast iron under welding conditions
of (90) A DC current (DCEN) and 20 volts. Welding wire type E- Ni -Fe- CI in diameter of
3.2mm was used and travel speed of 7 inch /min and welded through two passes. The weld
joined are examined using X-ray radiography, broken down joint are excepted. Corrosion
specimens prepared from free defects joints having measurements of (15*15*3) mm
agreeing to ASTM G71-31. Then Optical microscopy was employed to detect the welded
joint microstructure and base metal. Micro hardness was implemented using Vickers test.
Corrosion examinations are conducted using electrochemical potential state chamber in
equipped (sea water 3.5% NaCl),Corrosion examination is achieved using potentiostatic
polarization dimensions in saltwater 3.5%NaCl at potential scan rate (+100-100 mv/sec) to
estimate corrosion parameters by extrapolating. The corrosion rate was calculated by Tafel
equation. The results of corrosion rate can be predicted using a mathematical model using
data achieved from practical method and compare these results with the theoretical one,
results show that corrosion rate for welded joint is more than the base metal because of the
change in metal microstructure during welding process.