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| DSH 168A
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| Resistance to corrosion of current-carrying parts
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C6 v( y2 {1 n' ~$ y% G/ o. M | Generality& ^0 s# e. J" P9 s2 z7 i2 |3 q
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- n2 V- Q( c0 g9 k4 OQuestion:; O4 r8 ^# y/ V, f' k% P
How to judge whether a current-carrying part is resistant to corrosion ?
) y( O6 d( @5 u8 HDecision:( {# H0 P4 `0 U b5 o; r7 \$ P
CEE Recommendation n. 9 “Corrosion of current-carrying parts” may be applied to judge whether a current-carrying part is resistant to corrosion .3 d+ L6 @) s3 F# j
It is quoted in CB Bulletin No. 41 (September 1981).
8 L7 ^7 p6 v4 P- `In the following, for convenience, is reported a part of it:* h- c4 Q W) r7 H/ ?+ c N* T
RECOMMENDED TEXT, SCREWS, CURRENT-CARRYING PARTS AND CONNECTIONS.- v; ^& B3 C) K, y" S: P- F; B7 d% O
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.8 ^" D& G$ a' q
Compliance is checked by inspection and, if necessary, by measurement and by chemical analysis.
+ d+ P& Y8 O0 IAfter all the tests of the relevant specification, the current-carrying parts and parts of terminals shall show no appreciable deformation.
$ ]" M% s: J8 T) r! o+ |Examples of suitable metals, when used within the permissible temperature range and under normal conditions of chemical pollution, are:
: ~. Y n# Z* U3 ?- copper,
* \' s& L I* F; O- an alloy containing at least 58% copper for parts that are worked cold or at least 50% copper for other parts, c5 e9 G% U2 V' W+ Z" X5 _7 Z
- stainless steel containing at least 13% chromium and not more than 0,09% carbon,+ t: l v G F) i+ I; F
- steel provided with an electroplated coating of zinc according to ISO Publication 2081-1973, the coating having a thickness of at least:
9 R# J, w% }# Q9 a* 5 T ISO grade “1 mild” for ordinary equipment,$ f: p) N2 c& O2 s, q/ Y. X: W% b
* 12 T ISO grade “2 moderate” for jet-proof and splash-proof equipment,' v& Q3 |: H: e6 O7 ~ Z$ U6 _/ A
* 25 T ISO grade “3 severe” for jet-proof and watertight equipment.% G8 S4 r* e; K8 b. W4 B+ v
- 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:. {7 ~6 [& C4 g4 ?1 J+ U+ j
* service condition no. 2 for ordinary equipment,9 P: ?+ L% }1 }9 ?+ `6 M
* service condition no. 3 for drip-proof and splash-proof equipment,# }4 F& b" h" {7 O4 v) Z
* service condition no. 4 for jet-proof and watertight equipment.
4 b6 f4 ^3 `, t1 ]- 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;
2 j k" C( i5 s& J5 v6 j, ?7 Lhowever, 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.9 r; m: H) w5 d0 m- s2 {; m9 D
Zinc and other metals which are soft or liable to creep are not considered to be suitable for current-carrying parts and terminals .6 ~# Z% T" k! b+ {5 F
The thickness of the electroplated coatings on steel may be determined by the magnetic method described in ISO Publication 2178-1972, or by microscopical9 T$ h) q7 T8 M+ A D8 N T
measurement described in ISO Publication 1463-1973.
( Z$ X' V: v4 hb) 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 .8 x R" D+ d& V$ @6 ]
Compliance is checked by inspection.
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