CH606501

1421320 Electrolytic plating and anodizing of heating coils SIEMENS AG 21 June 1974 [26 July 1973] 27789/74 Heading C7B [Also in Division H5] An h.f. heating coil is electrolytically Al plated followed by anodizing and sealing the anodized layer. The coil may be pre-treated by: (i) pressureblasting with hard particles suspended in an inert gas or anhydrous aprotic liquid, (2) liquid drop bombardment with an inert anhydrous aprotic liquid or (3) by anodic removal of a thin surface layer in an 02-free, H 2 -free anhydrous aprotic organometallic bath, all as particulary described in Specification 1365009. The bath used in step (3) may be that used for Al plating and may contain AlEt 3 or AlMe3, plating being effected by polarity reversal. Other specified Al electrolytes are NaAlEt4, NaAlMe 4 , (alkyl) 4 N.AlEt 4 , Na/K.AlEt 4 , KF.2AlEt 3 , NaF.2À2AlEt 3 , (Me 3 C 6 H 5 CH 2 ) NCl.2À2AlEt 3 and Et 4 NCl.2À3AlEt 3 which may be used with up to 5 moles of a solvent such as toluene, benzene, xylene, THF, dipropyl or dibutyl ether or dioxanes. Plating may be effected under an N 2 or Ar blanket using pulsed current with a polarity reversal frequency of 10-200 c/s. Anodizing may be in a conventional H 2 SO 4 or oxalic bath followed by sealing in boiling water or steam. The coil may be a single or multiple spiral made of Cu, Al, brass or Ag (the latter being optionally a coating on Cu or brass) and is useful in zone-drawing semi-conductors.