What is critical crevice temperature?

The critical crevice temperature is the minimum temperature (°C) to produce crevice attack and CCT is usually lower than the critical pitting temperature (CPT). Computer software such as CRA-Compass can be used to assess the crevice corrosion resistance of an alloy for a given temperature and chloride concentration.

What is SCC in stainless steel?

Introduction to stress corrosion cracking (SCC) of stainless steels. Stress corrosion cracking (SCC) is the brittle failure at relatively low constant tensile stress of an alloy exposed to an environment. A synergistic action of corrosive environment and tensile stress on the material is required to cause SCC.

What causes SCC in carbon steel?

SCC usually occurs in certain specific alloy-environment-stress combinations. Stress corrosion cracking (SCC) is the cracking induced from the combined influence of tensile stress and a corrosive environment. The impact of SCC on a material usually falls between dry cracking and the fatigue threshold of that material.

What is SCC failure?

Stress corrosion cracking (SCC) is the growth of crack formation in a corrosive environment. It can lead to unexpected and sudden failure of normally ductile metal alloys subjected to a tensile stress, especially at elevated temperature.

What do you mean by crevice corrosion?

Crevice corrosion refers to the attack of metal surfaces by a stagnant solution in crevices, for example around the edges of nuts and rivet heads. When dust, sand and other corrosive substances are deposited on surfaces, they create an environment where water will accumulate and corrode the part.

What is the difference between pitting and crevice corrosion?

Whereas pitting corrosion occurs across the surface of a component, crevice corrosion is associated with a crevice, be that one that forms around a fastener, washer or joint, in a sharp corner or in an area where the flow of a liquid is slowed i.e. a dead spot.

What is SCC testing?

Stress corrosion cracking (SCC) is difficult to predict and identify, and it can lead to catastrophic failure, often without any prior warning. Element’s stress corrosion cracking capabilities can help to evaluate the susceptibility of metallic materials to cracking.

What causes cracks in metal?

Cracking usually occurs at temperatures at or near normal ambient. It is caused by the diffusion of hydrogen to the highly stressed, hardened part of the weldment. In low alloy steels, as the weld metal structure is more susceptible than the HAZ, cracking may be found in the weld bead.

How can SCC be avoided?

Prevention of Stress Corrosion Cracking

1. Avoid the chemical species that causes SCC.
2. Control of hardness and stress level (residual or load).
3. Introduce compressive stress by shot-peening for example.
4. Use of materials known not to crack in the specified environment.

What is the example of crevice corrosion?

Crevice corrosion is caused on contact of metals with metals or metals with nonmetals, for example, gaskets, couplings, and joints. It may occur also at washers, under barnacles, at sand grains, under applied protective films, and at pockets formed by threaded joints.

What is the mechanism of crevice corrosion?

Mechanism of crevice corrosion is similar to that of Pitting corrosion: dissolution of the passivating film and gradual acidification of the electrolyte caused by its insufficient aeration (Oxygen penetration). In presence of chloride ions corrosion proceeds by autocatalytic mechanism.