EP 0867530 B1 20000607 - Process and apparatus for coating metals
Title (en)
Process and apparatus for coating metals
Title (de)
Verfahren und Gegenstand für die Beschichtung von Metallen
Title (fr)
Procédé and dispositif pour le revêtement des métaux
Publication
Application
Priority
EP 97301617 A 19970311
Abstract (en)
[origin: EP0867530A1] The invention provides a process for forming a ceramic coating on a valve metal selected from the group consisting of aluminium, zirconium, titanium, hafnium and alloys of these metals. The process includes immersing the metal as an electrode in an electrolytic bath comprising an aqueous solution of an alkali metal hydroxide, providing an opposite electrode immersed in or containing the electrolyte liquid, passing a modified shaped-wave alternate electric current from a high voltage source of at least 700 V through a surface of the metal to be coated and the opposite electrode, wherein the modified shaped-wave electric current rises from zero to its maximum height and falls to below 40% of its maximum height within less than a quarter of a full alternating cycle, thereby causing dielectric breakdown, heating, melting, and thermal compacting of a hydroxide film formed on the surface of the metal to form and weld a ceramic coating to the metal, and changing the composition of the electrolyte while the ceramic coating is being formed, the change being effected by adding an oxyacid salt of an alkali metal. The invention also provides apparatus for carrying out this method.
IPC 1-7
IPC 8 full level
C25D 11/04 (2006.01); C25D 11/26 (2006.01)
CPC (source: EP)
C25D 11/04 (2013.01); C25D 11/26 (2013.01)
Designated contracting state (EPC)
AT BE CH DE DK ES FI FR GB GR IE IT LI LU MC NL PT SE
DOCDB simple family (publication)
EP 0867530 A1 19980930; EP 0867530 B1 20000607; AT E193735 T1 20000615; DE 69702238 D1 20000713; DE 69702238 T2 20010125
DOCDB simple family (application)
EP 97301617 A 19970311; AT 97301617 T 19970311; DE 69702238 T 19970311