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标题: DSH 168A Resistance to corrosion of current-carrying parts [打印本页]

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作者: 小米    时间: 2012-9-5 11:36
标题: DSH 168A Resistance to corrosion of current-carrying parts

DSH 168A 6 y$ _) r2 d/ k, K. Y

Resistance to corrosion of current-carrying parts 5 @. y& X5 t, L$ }9 p* L9 n

- # V, M3 z6 f6 U% ^5 c

Generality , j: N- }( y6 M2 V$ a6 ?2 X

Question:
How to judge whether a current-carrying part is resistant to corrosion ?
! L3 c1 r" Q) q0 [, HDecision:
) K, @- P2 [2 S1 M# d  QCEE Recommendation n. 9 “Corrosion of current-carrying parts” may be applied to judge whether a current-carrying part is resistant to corrosion .
$ y2 @: d2 ?! {" B* ~It is quoted in CB Bulletin No. 41 (September 1981).
; v4 ^2 S2 n/ `# `In the following, for convenience, is reported a part of it:
' w1 O7 A2 A5 G. T2 k8 ZRECOMMENDED 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.
& ^1 D) F4 b4 T8 h0 hCompliance is checked by inspection and, if necessary, by measurement and by chemical analysis.
# T/ k, e! c0 E3 M* z# E7 J2 NAfter 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:
) H% E! p. i+ G: w- copper,
' K/ ~  [2 y9 O3 v0 a- an alloy containing at least 58% copper for parts that are worked cold or at least 50% copper for other parts,
; F% J9 a1 h) m0 c- stainless steel containing at least 13% chromium and not more than 0,09% carbon,
* i" P8 T( l5 T7 J) E; O3 v  g2 G4 ?, D- steel provided with an electroplated coating of zinc according to ISO Publication 2081-1973, the coating having a thickness of at least:
6 B/ ]; Z: |( j% j0 f* 5 T ISO grade “1 mild” for ordinary equipment,
2 p3 N. `; Q+ o- [$ m* Y* 12 T ISO grade “2 moderate” for jet-proof and splash-proof equipment,
* 25 T ISO grade “3 severe” for jet-proof and watertight equipment.
' u1 [' [3 h$ v; d+ k! _2 M+ b+ }- 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:
0 B* A- H4 B6 X+ }, B* H* service condition no. 2 for ordinary equipment,
! t$ F( m  @8 x- ~# A6 D3 }) ]% L* service condition no. 3 for drip-proof and splash-proof equipment,
* service condition no. 4 for jet-proof and watertight equipment.
+ K  O' }$ Q9 b1 t6 f2 |; B- 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;
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.
  c2 w/ {8 E8 Y% [6 d' RZinc 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.
b) 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 .
5 Y: T/ n4 z$ _/ I0 ~: T$ cCompliance is checked by inspection.

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