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ETANCO-SOLARFIXINGS


Stress corrosion This involves a type of corrosion that occurs almost entirely without corrosion


products and is therefore extremely dangerous. It only occurs when the material surface is subject to tensile stress, a specifi c medium is present (chloride ions) and the material is vulnerable to this kind of corrosion. The austenites with approx. 8% to 12% nickel principally belong to these vulnerable materials and dramatic cases of damage have been reported. However, stress corrosion is of little signifi cance for screws used in the construction industry. Nonetheless, in critical application cases one should also not neglect this here, especially when used in swimming pools.


Countermeasures: increase or reduce Ni content In order to prevent stress corrosion in corrosion-resistant austenitic steels, one


must either increase or reduce the nickel content. However, increasing the nickel content leads to a signifi cant increase in price, while a reduction means that there is no longer an austenitic structure present, and thus all of the advantages of the austenites are lost. However, it can principally also be said of this type of corrosion that an increase of the pitting index, meaning the addition of Mo (V4A), reduces the danger of the initiation of cracks and thus of corrosion.


Table 1 (above) compiles several selected austenitic materials with their resistance SK PLUS


class against corrosion. It can be seen that the screw groups A2, A2L and A3 correspond to steel type V2A and the screw groups A4, A4L and A5 to steel type V4A. One can also see with the help of the family tree in Table 2 (below) that, for example, the material 1.4404 has two decisive advantages relative to the material 1.4301. The alloying of Mo means that the material is imbued with signifi cantly improved resistance against general corrosion, pitting corrosion and crevice corrosion due to its higher pitting index and can thus also be used for inaccessible constructs and subjected to moderate chloride and sulphur dioxide stresses. The removal of C avoids the danger of intercrystalline corrosion.


ETANCO GmbH Auf der Landeskrone D-57234 Wilnsdorf-Wilden


Tel.: 0049 27 39 / 47 99 64 Fax: 0049 27 39 / 47 99 66


Mail: info@etanco.de Web: www.etasol-solar-zubehoer.de www.etanco.de


Inferences for the use of screws Even for constructs subject to moderate chloride and sulphur dioxide stresses


(industrial atmosphere) and generally for inaccessible constructions, screws of the material groups A4 (1.4401), A4L (1.4404) or A5 (1.4571) can be used due to their signifi cantly better resistance to corrosion. This results from the corrosion resistance of the steels and is refl ected in building regulations.


Solar Saddle Washer with Technical Approval


The 1 st


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