Surface Chemical Factors in the Stress-Corrosion Cracking off Alpha Brass

CORROSION ◽  
1966 ◽  
Vol 22 (6) ◽  
pp. 178-179 ◽  
Author(s):  
H. E. JOHNSON ◽  
J. LEJA
Keyword(s):  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Absolute Temperature ◽  
Corrosion Cracking ◽  
General Corrosion ◽  
Linear Relationships ◽  
Energy Lowering ◽  
Cracking Mechanisms ◽  
Ph Range ◽  
Alpha Brass

Abstract Stress corrosion cracking of alpha brass in ammonia solutions containing copper-ammonia complexes is most rapid in the pH range 6 to 7, where weight loss corrosion is insignificant, Linear relationships were found for (a) log 1/tc (tc = cracking time) vS log Cu++ (initial copper concentration) and (b) l/tc vs 1/T (T = absolute temperature). Oxygen appears necessary for general corrosion and cracking at pH values above 8. Rapid cracking is interpreted in terms of a drastic surface free energy decrease caused by the adsorption of an intermediate copper-zinc- ammonia complex (not yet identified) which is catalytically formed at the brass/solution interface and is surface active. It is suggested also that linear relationships like (a) and (b) above may be distinguishing features of stress corrosion cracking mechanisms which involve surface energy lowering.

Film and pH Effects in the Stress Corrosion Cracking of Type 304 Stainless Steel

CORROSION ◽  
1970 ◽  
Vol 26 (10) ◽  
pp. 420-426 ◽  
Author(s):  
H. R. BAKER ◽  
M. C. BLOOM ◽  
R. N. BOLSTER ◽  
C. R. SINGLETERRY
Keyword(s):  
Stainless Steel ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking ◽  
304 Stainless Steel ◽  
Corrosion Mechanism ◽  
General Corrosion ◽  
Protective Film ◽  
Corrosion Resistant ◽  
Ph Range

Abstract Rapid stress corrosion cracking of 304 stainless steel in MgCl2-FeCl3 solutions at 125 C has been shown to occur only when the pH of the corrodent liquid within the crack lay between 1.2 and 2.5. A film of more acidic corrodent solution is raised to pH = 1.2 by reaction with the metal within a few seconds after isolation in a pit, crack, or crevice. MgCl2 solutions of pH higher than 2 became more acidic when in contact with stainless steel as a result of corrosion processes. The pH of small amounts of such solution isolated in pits or crevices eventually fell to near 1.5, where stress corrosion cracking could occur. This pH range is considered to be critical for stress corrosion cracking of 304 stainless steel because it is the range in which a corrosion resistant protective film is formed in the presence of the corrodent solution. This film is essential to crack propagation. If there is added to a corrodent , solution in this pH range an organic complexing agent such as glycerine or glycol which prevents-formation of the protective oxide film, the general corrosion process continues unchecked but no stress corrosion cracking occurs. The data support a model in which stress corrosion cracking is driven by a highly localized galvanic cell within the crack. The cell operates in such a way that there is no large change in pH of the solution in the crack. These results emphasize the importance of the corrosion resistant film in the chemical aspect of the stress corrosion mechanism.

scholarly journals Effect of pH on Stress Corrosion Cracking of 6082 Al Alloy

Metals ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 578 ◽  
Author(s):  
C. Panagopoulos ◽  
Emmanuel Georgiou ◽  
K. Giannakopoulos ◽  
P. Orfanos
Keyword(s):  
Aluminum Alloy ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking ◽  
Al Alloy ◽  
Cracking Behavior ◽  
Effect Of Ph ◽  
Cracking Mechanisms ◽  
6082 Aluminum Alloy ◽  
6082 Al Alloy

In this work, the effect of pH (3, 7 and 10) on the stress corrosion cracking behavior of 6082 aluminum alloy, in a 0.3 M sodium chloride (NaCl) aqueous based solution was investigated. The stress corrosion cracking behavior was studied with slow strain rate testing, whereas failure analysis of the fractured surfaces was used to identify the dominant degradation mechanisms. The experimental results clearly indicated that stress corrosion cracking behavior of this aluminum alloy strongly depends on the pH of the solution. In particular, the highest drop in ultimate tensile strength and ductility was observed for the alkaline pH, followed by the acidic, whereas the lowest susceptibility was observed in the neutral pH environment. This observation is attributed to a change in the dominant stress corrosion cracking mechanisms.

About the Role of Hydrogen in Stress Corrosion Cracking of a 7xxx Aluminium Alloy (Al-Zn-Mg)

2016 ◽  
Vol 877 ◽  
pp. 522-529 ◽  
Author(s):  
Loïc Oger ◽  
Eric Andrieu ◽  
Grégory Odemer ◽  
Lionel Peguet ◽  
Christine Blanc
Keyword(s):  
Mechanical Properties ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Local Stress ◽  
Corrosion Cracking ◽  
Hydrogen Trapping ◽  
Stress Tests ◽  
Fracture Modes ◽  
Cracking Mechanisms ◽  
Local Stress State

The effects of hydrogen during stress corrosion cracking mechanisms (SCC) have been highlighted for many years but hydrogen trapping mechanisms are not yet well understood for 7xxx aluminium alloys. The 7046-T4 Al-Zn-Mg alloy has been chosen for this study because its low corrosion susceptibility allows hydrogen embrittlement (HE) to be more easily distinguished during SCC tests. Tensile stress tests have been carried out at a strain rate of 10-3 s-1 on tensile samples after an exposure at their corrosion potential in a 0.6M chloride solution for 165 hours under an imposed loading of 80%Rp0.2. The results were compared to those obtained for samples pre-corroded without mechanical loading applied and healthy specimens. A loss of mechanical properties was observed for the pre-corroded samples and presumably attributed to the absorption, the diffusion and the trapping of hydrogen which affects a volume under the surface of the alloy and modifies its mechanical properties. Scanning electron microscope (SEM) observations highlighted a strong effect of hydrogen on fracture modes. The ductile-intergranular initial fracture mode observed on the healthy samples was partially replaced for the pre-corroded samples by a combination of two main fracture modes, i.e. brittle intergranular and cleavage, in relation with the nature of the hydrogen trapping sites and local stress state.

Sign in / Sign up

Export Citation Format

Share Document