Crevice corrosion is a form of localised corrosion that occurs in narrow, poorly ventilated gaps - for example between threaded connections, overlaps or under seals and paintwork. The restricted access of oxygen creates electrochemical differences to the surrounding medium, which cause targeted material attack.

High-alloy steels and stainless steel, which are otherwise considered highly resistant to corrosion, are particularly affected. Crevice corrosion can progress unrecognised for a long time and considerably shorten the service life of components.

Oxygen depletion occurs inside a crevice. The environment remains rich in oxygen, resulting in a concentration gradient. This gradient leads to an accumulation of aggressive ions (e.g. chloride) and a locally lowered pH value.
The result: an electrochemically active zone forms, which dissolves the metal at certain points - the typical starting point for crevice corrosion.

Whether and how quickly crevice corrosion occurs depends on several factors:

• Material: Not all stainless steels are equally resistant. Molybdenum-containing steels resist chlorides longer.

• Slit geometry: depth, width and length influence oxygen transport and ion concentration.

• Medium: Salinity, temperature and pH value intensify the effect.

• Operating conditions: Stagnation and stagnant medium favour crevice corrosion.

• Coatings: Infiltrated coatings can also become a gap.

Crevice corrosion often occurs where liquid penetrates into narrow spaces and can no longer escape:

• Screw and flange connections

• Overlapping of sheets or profiles

• Pipe clamps and pipe supports

• Seals, washers, drill holes

• Under coatings or paints

Marine and offshore applications are particularly affected. Salty air and splash water in harbours, on ships or offshore platforms significantly accelerate crevice corrosion on pipe clamps, screw connections and fastenings. Well thought-out corrosion protection is crucial here.

There are numerous potential crevice areas on pipes in challenging environments:

• pipework and fittings

• Control blocks and flanges

• Attachment points for units

• Concealed areas under seals or layers of paint

Especially in offshore and marine applications, where seawater and salty air are omnipresent, there is an increased risk of crevice corrosion.

Prevention starts at the design stage:

• Constructive design: Avoid gaps or design them so that they are self-draining.

• Material selection: Select corrosion-resistant steels or coatings.

• Sealing: Seals and elastic elements prevent the penetration of liquids.

• Regular maintenance: Remove deposits and moisture.

• Protective coatings: Lacquers or galvanised coatings should bridge gaps where possible.

STAUFF relies on comprehensive corrosion protection for its components - from the choice of materials and coatings to intelligent design solutions:

• High-quality materials: V4A stainless steel or optimised surface coatings ensure long-term durability.

• Clean production and packaging: To avoid contamination, components are supplied in sealed packaging units.

• Special fastening solutions: STAUFF ACT clamps - Anti Corrosion Technology:
  ACT clamps are specially designed to protect stainless steel pipework against crevice corrosion. Flame-retardant polypropylene (PP-V0) with integrated elastomer strips prevents moisture from penetrating between the clamp and the pipe. All metal parts are made of V4A stainless steel and are optimised for seawater resistance. Flexible installation options - such as weld plate or surface mounting - facilitate integration.
  This means that pipework can be reliably fastened even in aggressive environments.

When selecting components, the following points should be taken into account:

• Material and standards: Stainless steel quality, coatings, EN standards for corrosion resistance.

• Gap geometry: If possible, open constructions or complete sealing.

• Medium and environment: Chloride-containing media, seawater and high temperatures accelerate corrosion.

• Accessories: protective caps, seals, elastomer strips.

Careful selection ensures that components work reliably and have a long service life.

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