(19)

(11)

EP 0 072 789 A1

(12)

(43) Date of publication: 02.03.1983 Bulletin 1983/09 (21) Application number: 81900435.0 (22) Date of filing: 18.02.1981

(51) International Patent Classification (IPC):  C21D 1/ 46( . ) C23C 8/ 44( . ) (86) International application number: PCT/GB1981/000022 (87) International publication number: WO 1982/002905 (02.09.1982 Gazette 1982/21)

(84) Designated Contracting States: AT CH DE FR LI LU NL SE (71) Applicant: NATIONAL RESEARCH DEVELOPMENT CORPORATION London SE1 6BU (GB)	(72) Inventor: KERRIDGE, David Henry Salisbury Wiltshire (GB)