What is the most likely cause of intergranular corrosion?

Intergranular corrosion (IGC)

It is as a result of chromium depletion, mainly due to the precipitation of chromium carbides in the grain boundaries. Chromium carbides can be precipitated if the stainless steel is sensitized in the temperature range 550–850°C (1020–1560°F), for example during heat treatment or welding.

What causes intergranular corrosion in aluminum alloys?

IGC of commercial alloys is generally caused by enrichment or depletion of alloying elements in the area adjacent to the grain boundaries, by intergranular precipitation of second-phase particles or by the presence of alloy impurities segregated at the grain boundaries.

What happens during intergranular corrosion?

Intergranular corrosion is localized attack along the grain boundaries, or immediately adjacent to grain boundaries, while the bulk of the grains remain largely unaffected.

What is the mechanism of intergranular corrosion?

Intergranular corrosion is caused by Microsegregation of impurities and alloying elements on the grains boundaries. The driving force of intergranular corrosion is the difference between the Electrode potentials of the grain boundary and the grain itself, which form a galvanic cell in presence of an electrolyte.

How can we prevent intergranular corrosion?

Intergranular corrosion can be prevented through:
  1. Use low carbon (e.g. 304L, 316L) grade of stainless steels.
  2. Use stabilized grades alloyed with titanium (for example type 321) or niobium (for example type 347). Titanium and niobium are strong carbide- formers. …
  3. Use post-weld heat treatment.

Who shows intergranular corrosion?

Intergranular corrosion occurs as the name indicates along grain boundaries on. This corrosion form is sensitive to high carbon contents in the stainless steel and occurs if chromium carbides are precipitated in between the grains. Precipitation reactions in stainless steels can be read about in Section 3.04.

What causes stress corrosion?

Stress-corrosion occurs when a material exists in a relatively inert environment but corrodes due to an applied stress. The stress may be externally applied or residual. … Stress corrosion is a form of galvanic corrosion, where stressed areas of the material are anodic to the unstressed areas of the material.

What causes hydrogen embrittlement?

Hydrogen Embrittlement occurs when metals become brittle as a result of the introduction and diffusion of hydrogen into the material. The degree of embrittlement is influenced both by the amount of hydrogen absorbed and the microstructure of the material.

What are the methods used in identifying the intergranular corrosion?

The five intergranular corrosion testing methods within ASTM A262 are:
  • The Oxalic Acid Test.
  • The Strauss Test.
  • The Huey Test.
  • The Streicher Test.
  • The Copper Sulfate Test.

What causes hydrogen induced breaking?

Hydrogen Induced breaking (HIC) is a common form of wet H2S breaking caused by the blistering of a metal due to a high concentration of hydrogen. … The damage occurs when the hydrogen collects at inclusions or impurities in the steel.

What are the 3 types of corrosion?

CORROSION TYPES And Prevention
  • Uniform Corrosion. Uniform corrosion is considered an even attack across the surface of a material and is the most common type of corrosion. …
  • Pitting Corrosion. …
  • Crevice Corrosion. …
  • Intergranular Corrosion. …
  • Stress Corrosion breaking (SCC) …
  • Galvanic Corrosion. …
  • Conclusion.

Which is most responsible for stress corrosion?

Chloride stress corrosion is a type of intergranular corrosion and occurs in austenitic stainless steel under tensile stress in the presence of oxygen, chloride ions, and high temperature. It is thought to start with chromium carbide deposits along grain boundaries that leave the metal open to corrosion.

What causes cold breaking in welds?

This occurs when steel is rapidly cooled and allowed to form martensite. Due to the rapid cooling, hydrogen atoms trapped inside of the heat-affected zone join together and create an internal stress on the weldment. This stress, combined with a brittle microstructure like martensite, causes breaks to form.

What is embrittlement?

brittle
Embrittlement is the partial or complete loss of a material’s ductility, thus making it brittle. … Embrittlement in steel can be associated with strain aging. This refers to the delayed increase in strength and hardness, impact resistance and loss of ductility.

Does hydrogen cause corrosion?

With hydrogen damage, multiple metal degradation processes occur due to interaction with hydrogen. For example, in boiler tubes, hydrogen damage is caused by a corrosive reaction between steam and steel, resulting in decreased material strength and localized corrosion.

What is HAZ breaking?

An underbead break, also known as a heat-affected zone (HAZ) break, is a break that forms a short distance away from the fusion line; it occurs in low alloy and high alloy steel. The exact causes of this type of break are not completely understood, but it is known that dissolved hydrogen must be present.

Where does cold breaking occur?

Hydrogen breaking may also be called cold breaking or delayed breaking. The principal distinguishing feature of this type of break is that it occurs in ferritic steels, most often immediately on welding or a short time after welding.

How does preheating prevent cold breaking?

Preheat. Preheat, which slows the cooling rate, allows some hydrogen to diffuse away, and generally reduces the hardness, and therefore susceptibility to breaking, of hard, crack-sensitive microstructural regions.