Corrosion behavior of laser and TIG welded austenitic stainless steel

The corrosion behaviour and the effect of microstructural changes of 304 austenitic stainless steel induced by the processes of gas tungsten arc welding [GTAW] or TIG and laser beam welding [LBW] have been investigated. For each experiment, base metal and heat affected zone [HAZ] have been selected. The microstructure and the phases present in the HAZ of the laser and TIG weld specimens were investigated and analyzed by optical microscopy, scanning electron microscopy and energy dispersive X-ray. Very fine grains were formed at the HAZ in comparison to the base metal carbide precipitations formed at the grain boundaries. Beside the main austenite phase a ferrite phase is present at the HAZ at the grain boundaries and inside the grain. The ferrite content was higher in laser weld zone than TIG weld zone. Electrochemical measurements using poteniodynamic cyclic polarization in 0.5M NaCI solution have been carried out for welded and unwelded specimens. The pitting potential was estimated reflecting higher pitting resistance for base metal than laser and TIG weld, respectively. The decrease in pitting resistance for laser and TIG weld could be related to the presence of carbide and ferrite phases in their microstructure

Corrosion inhibition of Cu in nitrate solution

The effect of ethylenediamine [ED] and acetic acid on the corrosion inhibition of copper in 0.1 M NaNO] was studied. The study involved electrochemical polarization methods, gravimetric measurements and scanning electron microscopy investigations [SEM]. Both of ED and concentrated solutions of acetic acid >/= 10[-3] M act as a promoter while diluted concentrations of acetic acid

Corrosion behaviour of some stainless steels in chloride solutions

The pitting corrosion of various types of stainless steels was studied in different anions. The effect of temperature was also examined. The most well known aggressive anion is the chloride ion. The open circuit potential and the potentiodynamic techniques were used. The pitting potential, Ep and the protection potential, Epp were determined for stainless steels.The pitting and protection potentials depend linearly on the concentration of Cl - ion according to the equations. Ep = a + b log [Cl -]. Epp=a -+b - log [Cl -]. Pitting potential is shifted to more negative values with the increase of Cl - content, as well as the temperature according to the composition of the alloy. The concentration necessary for pitting and the critical pitting temperature increases with increasing Cr content. The effect of different concentrations of SO 4 -2 ion at temperature up to 80°C was also investigated

Zinc-steel polarity reversal. I. Effect of bicarbonate concentration and temperature

The open circuit potentials of 2 types of zinc and mild steel were followed with time in different NaHCO3 solutions [10-5-10-1 M] at different temperatures [25-80 degree]. No potential reversal of polarity was observed between zinc and mild steel at room temperature. At higher temperatures, passivation of zinc and mild steel would preferentially occur, and potential reversal was manifested, particularly for pure zinc. Impurities, even in minute amounts, enhanced the activation of zinc, as well as sodium hydroxide at adequate concentration even in presence of the bicarbonate. AES survey analysis of the electrode surface gave more insight on the corrosion products