Stress corrosion cracking (SCC) is characterized by cracks propagating either transgranularly or intergranularly (along grain boundaries). Chlorides are widely present in many industrial and natural environments, such as seawater. When metal alloys are exposed to these environments, they can become vulnerable to Chloride-induced SCC. This type of corrosion is particularly common in materials like stainless steel, nickel alloys, and aluminium alloys.

One of the key features of Chloride-induced SCC is that it can occur even in the absence of external corrosion. This means that even though the surface of the metal may appear to be in good condition, internal cracks can form, making the material weaker and more susceptible to failure.

Chloride-induced SCC can have significant safety and economic consequences, especially in critical applications such as pipelines, pressure vessels and offshore platforms.

The risk of SCC increases with increasing temperature, increasing concentration of chloride and decreasing pH value of the environment.

Duplex stainless steels with a combination microstructure of austenite and ferrite have much better Chloride-induced SCC resistance than that of the classic austenitic grades.

Stress corrosion cracking (SCC) results from the combined action of three factors:

• Tensile stresses in the material
• A corrosive medium – especially chloride-bearing media. Chloride-induced SCC normally occurs above 60°C (140ºF).
• The use of material susceptible to stress corrosion cracking (SCC)

A precursor of stress corrosion cracking in chloride-bearing environments is pitting corrosion, occurring if the stainless steel is not sufficiently resistant to pitting.

Testing to Chloride-induced SCC resistance

Chloride-induced SCC is tested experimentally in the laboratory using a chloride-containing environment. Testing can be carried out, for example, in boiling 40% CaCl₂ or chloride-containing water.

Materials with high resistance to chloride-induced stress corrosion cracking (SCC).

Duplex stainless steels, nickel based steels and austenitic stainless steels with a high nickel content (> 25%). Ferritic steels are also resistant to cracking but may corrode.

Typ of material	EN no.	UNS no.	PREN*	™ Trademarks
Standard Duplex	1.44621)	S31803	35	SAF 2205® UR™ 2507
Super Duplex	1.4410	S32750	43	Forta SDX 2507 SAF 2507 DX2507
Super Duplex	1.4501	S32760	42	Forta SDX 100 Zeron® 100 SAF32760  UR™ 2507W
Hyper Duplex	1.4658 –	S32707 S33207	49 50	SAF 2707 HD® SAF 3207 HD®
Ni-based alloy	2.4602	N06022	66	INCONEL® alloy 22 Hastelloy® C-22
Ni-based alloy	2.4819	N10276	70	INCONEL® Alloy C-276 HASTELLOY® C-276
Ni-based alloy	2.4856	N06625	51	INCONEL® Alloy 625 HAYNES® 625 alloy VDM® Alloy 625
Ni-based alloy	2.4643	N06035	60	HASTELLOY® G-35
Super austenitic stainless	1.4547	S32654	43	Ultra 254 SMO® UR ™ 254
Super austenitic stainless	1.4529	N08926	45	Ultra 6XN® AL-6XN® VDM® Alloy 926 UR ™ 367
Super austenitic stainless	1.4539	N08904	33	ATI 904L™ Ultra® 904L UR™ 904L VDM® Alloy 904 L

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