Crevice corrosion

Crevice corrosion occurs on metal parts in the presence of a corrosive medium in narrow, non-closed gaps such as overlaps, attached webs and weld seams that are not welded through . The driving force is the difference in concentration between the medium in the gap and the area outside the gap, which are caused by the diffusion of the reactants that is inhibited in the gap . The potential difference associated with the difference in concentration leads to electrochemical corrosion in the gap ( hydrogen type ) or its immediate surroundings ( oxygen type ).

Even stainless CrNi steels can corrode in crevices if there is no oxygen available to form the protective oxide layer.

The selection of a corrosion-resistant material is usually the most economical way of avoiding corrosion. Crevice corrosion can also be prevented by constructively dispensing with gaps or by making them so large that the diffusion of the media is not hindered. In DIN EN 12502-4 "Corrosion protection of metallic materials - influencing factors for stainless steels" it is advised to make the gap widths greater than 0.5 mm in order to avoid gap corrosion, but apart from the gap width, the gap depth is also important. In addition, structurally unavoidable gaps can be sealed with plastics ; This principle is used when connecting screws and nuts at risk of corrosion, which are secured against unintentional loosening by an adhesive and protected against crevice corrosion.

literature

• Johannes Barz: Crevice corrosion of various metallic materials. 1st edition, Grin Verlag 2010.
• Helmut Kaesche: The corrosion of metals. Third edition, Springer Verlag, Berlin / Heidelberg 1990, ISBN 3-540-51569-0 .

• Dubbel, Taschenbuch für den Maschinenbau, 14th edition, Section E1.2.3 on page 257 and F4.3.5 on page 329

See also

• Corrosion element

Web links

• Types of corrosion - Part 2 (accessed September 6, 2018)
• Corrosion in stainless steels (accessed September 6, 2018)
• Stainless Steel and Corrosion (accessed September 6, 2018)
• Corrosion (accessed September 6, 2018)
• Corrosion protection, analysis of existing steel structures (accessed on September 6, 2018)

Individual evidence

1. ↑ Hans-Dieter Jakubke, Ruth Karcher (coordinators): Lexikon der Chemie in three volumes, Spektrum Verlag, Heidelberg, Volume 3, 1999, ISBN 3-8274-0381-2 , p. 250.