DSH 168A Resistance to corrosion of current-carrying parts

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DSH 168A + W8 e; H, t* ], U* d4 [

Resistance to corrosion of current-carrying parts & x8 v& P7 s" Z0 z! I

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Generality . ?8 A$ z% a9 {- V3 ~; I. v8 ?

& J' s' {3 x, V* v% cQuestion:
' M1 r( d  M* ^! g5 AHow to judge whether a current-carrying part is resistant to corrosion ?
8 F+ g, q5 }$ Q; B4 Z+ O* {Decision:
CEE Recommendation n. 9 “Corrosion of current-carrying parts” may be applied to judge whether a current-carrying part is resistant to corrosion .
It is quoted in CB Bulletin No. 41 (September 1981).
In the following, for convenience, is reported a part of it:
RECOMMENDED TEXT, SCREWS, CURRENT-CARRYING PARTS AND CONNECTIONS.
a) Current-carrying parts and parts of terminals shall be of a metal having, under the conditions occurring in the equipment, adequate mechanical strength and resistance to corrosion.
5 D$ D2 Z9 c3 [Compliance is checked by inspection and, if necessary, by measurement and by chemical analysis.
$ z+ u5 a+ f  `7 `5 gAfter all the tests of the relevant specification, the current-carrying parts and parts of terminals shall show no appreciable deformation.
Examples of suitable metals, when used within the permissible temperature range and under normal conditions of chemical pollution, are:
- copper,
% Y9 C9 s3 x4 f+ D- an alloy containing at least 58% copper for parts that are worked cold or at least 50% copper for other parts,
# y7 l# U& F" V- A& b( t- stainless steel containing at least 13% chromium and not more than 0,09% carbon,
- steel provided with an electroplated coating of zinc according to ISO Publication 2081-1973, the coating having a thickness of at least:
* 5 T ISO grade “1 mild” for ordinary equipment,
) i7 q6 A7 z: ]7 N2 l* Q! m8 N* 12 T ISO grade “2 moderate” for jet-proof and splash-proof equipment,
# z; z  T: J) n* [* 25 T ISO grade “3 severe” for jet-proof and watertight equipment.
- steel provided with an electroplated coating of nickel plus chromium according to ISO Publication 1456-1974, the coating having a thickness at least equal to that specified for:
* service condition no. 2 for ordinary equipment,
* service condition no. 3 for drip-proof and splash-proof equipment,
7 w: i: h' q" H; w; C: t3 Q: q9 L; v* service condition no. 4 for jet-proof and watertight equipment.
- Aluminium and its alloys, provided special measures are taken for removing, where necessary, the oxide layer, for obtaining a sufficient and durable contact pressure and for ensuring that the point of connection withstands the corrosion test specified;
5 O9 U. C& z! F* O, Q9 ]) f% ^however, until a suitable corrosion test and an electrical performance test are available, aluminium and its alloys should preferably not be used for current-carrying parts and terminals within the equipment.
+ b+ V6 ?1 |* @; {6 G9 [Zinc and other metals which are soft or liable to creep are not considered to be suitable for current-carrying parts and terminals .
The thickness of the electroplated coatings on steel may be determined by the magnetic method described in ISO Publication 2178-1972, or by microscopical
measurement described in ISO Publication 1463-1973.
# U4 V; i- g" y* Lb) Under moist conditions, metals showing a great difference of electrochemical potential with respect to each other shall not be used in contact with each other .
Compliance is checked by inspection.



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