Effects of Sulfur Compounds on the Pitting Behavior of Type 304 Stainless Steel in Near-Neutral Chloride Solutions

CORROSION ◽  
1982 ◽  
Vol 38 (5) ◽  
pp. 261-265 ◽  
Author(s):  
R. C. Newman ◽  
H. S. Isaacs ◽  
B. Alman
Keyword(s):  
Stainless Steel ◽  
Chloride Solution ◽  
Surface Deformation ◽  
304 Stainless Steel ◽  
Pitting Potential ◽  
Acidic Solutions ◽  
Type 304 ◽  
Type 304 Stainless Steel ◽  
Sulfur Containing ◽  
Effect Of Surface

Abstract Pitting potentials have been measured potentiodynamically for Type 304 stainless steel in neutral or mildly acidic solutions containing 0.25M NaCl and various concentrations of sulfur species from 0 to 2 molar. Additions of 0.01 to 0.02M Na2S2O3 lowered the pitting potential by more than 300 mV, while additions of more than 0.5M Na2S2O3 inhibited pitting. KSCN showed similar but less marked effects, while increasing Na2S additions up to 0.1 molar (giving H2S and HS− at neutral pH) caused an increasing reduction in the pitting potential. Additions of Na2S4O6 up to 0.05M promoted pitting, but addition of 0.01 M Na2SO3 had no effect. Parallel pitting potential measurements using a scratch technique gave lower values for the sulfur containing solutions but a higher value for the plain chloride solution; this effect of surface deformation was also reflected in the results obtained potentiodynamically on abraded and electropolished surfaces.

Stress Corrosion Cracking of Sensitized Type 304 Stainless Steel in High Temperature Chloride Solutions

CORROSION ◽  
1981 ◽  
Vol 37 (11) ◽  
pp. 616-627 ◽  
Author(s):  
L. F. Lin ◽  
G. Cragnolino ◽  
Z. Szklarska-Smialowska ◽  
D. D. Macdonald
Keyword(s):  
Stainless Steel ◽  
Strain Rate ◽  
Potential Temperature ◽  
Slow Strain Rate ◽  
304 Stainless Steel ◽  
Pitting Potential ◽  
Critical Potential ◽  
A Value ◽  
Type 304 ◽  
Type 304 Stainless Steel

Abstract The SCC susceptibility of sensitized Type 304 stainless steel was studied using slow strain rate tests in 0.01 M NaCl as a function of applied potential at temperatures ranging from 100 to 250 C. Potential-temperature domains in which purely IGSCC, simultaneous IGSCC and TGSCC, and IGSCC accompanied by pitting corrosion have been determined. A critical potential for IGSCC and its dependence upon temperature was measured. This critical potential is equal to the pitting potential at temperatures lower than 150 C, but at higher temperatures, it lies within the passive range of the alloy. Above 150 C, the potential for breakdown of passivity becomes independent of temperature and corresponds to the potential at which TGSCC occurs on sensitized and on quench-annealed material. Interrupted slow strain rate tests were conducted to determine the time at which intergranular cracks start to propagate. On the basis of these data, average intergranular crack propagation rates were calculated. An apparent activation energy of 29 ± 12 KJ/mol was determined in the temperature range 200 to 275 C. It was also found that propagating intergranular cracks can be arrested by changing the potential to a value which is lower than the critical potential.

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