Process for Safe, Efficient Cleaning of Titanium And Other Metal Deposits off Stainless Steel
Original Publication Date: 1991-Apr-01
Included in the Prior Art Database: 2005-Apr-02
An efficient chemical cleaning method is described which removes titanium admixed with other metal deposits from stainless steel without causing titanium fires or explosions.
Process for Safe, Efficient Cleaning of Titanium And
Deposits off Stainless Steel
chemical cleaning method is described which
removes titanium admixed with other metal deposits from stainless
steel without causing titanium fires or explosions.
copper, titanium, nickel, gold, and other metals are
deposited in layers on ceramic substrates or on semiconductors.
These deposits are applied in evaporators or sputterers. During such
operations the inside surfaces of the tools become coated with
various layers of metal. The stainless steel tool sets must be
cleaned of these metals without etching the steel or setting off a
titanium explosion or fire. One type of explosion occurs when a set
containing too much titanium in the layering is immersed in a first
etch of nitric acid of too high concentration. Chromium, gold, or
titanium will not react with nitric acid, but any copper or nickel
present will [*], resulting in a large volume of rapidly expanding
gaseous nitrogen oxides. The confinement of this gas by inert
titanium or gold layers will often result in an explosion. The shock
can also ignite the titanium metal, adding to the explosive force.
Another type of explosion can occur when a part coated with a matrix
of copper, nickel, and titanium is first etched in nitric acid and
withdrawn. On contact with the air the remnant titanium, of high
surface area and stripped of its protective, inerting matrix of
copper and/or nickel, will frequently and unpredictably explode. The
titanium may also explode in a subsequent bead blasting step.
This new cleaning method avoids thes...