Armco Inc.

Armco Steel Company, L.p.

Ashok Sabata

Wim J Van Ooij

Joseph A Douthett

Sherman E Winkle, Sr

Ricole A Edwards

A stainless steel sheet suitable for use in the manufacture of an exhaust component. The steel sheet has at least one surface pretreated with a protective coating resistant to delamination at temperatures up to about 540.degree. C. including an inner inorganic portion and an outer organic portion. The inorganic portion includes at least 50 mg/m.sup.2 of a chromium based conversion coating having a thickness no greater then 0.02 mm. The conversion coating contains particulate silica with the weight ratio of chromium to silica within the range of 1:1 to 2:1. The outer organic portion includes a silicone paint containing 40-60 wt. % silicone resin. The silicone paint is dried at a temperature less than 300.degree. C. in less than one minute and then coated with a copolymer of a thermoplastic acrylic and a lubricant or a polymeric olefin. The acrylic copolymer contains 5-70 wt. % of the lubricant and the polymeric olefin contains 90% olefin resin. The lubricant coated steel sheet then is dried at a temperature of a 25.degree.-120.degree. C. for less than one minute to form a film thickness of 0.0005-0.020 mm, having a coefficient of friction of no greater than about 0.05 and a weight of 10-5000 mg/m.sup.2. The dried silicone paint covered by the dry lubricant film is tack-free, impervious to moisture, oil, dirt, and the like with the silicone coated steel sheet ready for forming into an exhaust component with minimal delamination of the dried silicone paint without additional external lubricant being required on the sheet.

Precoated chromium alloyed steel with enhanced paint adhesion for

Painted metal sheet pretreated with a composite coating including an insoluble, inorganic inner layer and an organic outer layer. The inorganic layer is formed by rinsing the sheet with an alkaline solution containing at least 0.005M of at least one of a dissolved silicate or a dissolved aluminate. The sheet is dried to form an inorganic layer having a thickness of at least 2 .ANG.. The inorganically coated sheet then is rinsed with a solution containing at least 0.1 vol.-% of a hydrolyzed silane and at least 0.02 vol.-% of a hydrolyzed crosslinking agent. The silane treated sheet is dried to form a siloxane layer having an average thickness at least 5 .ANG.. After being painted, the siloxane layer forms an adherent bond between the paint and the metal substrate. The metal preferably is a chromium alloyed steel and may be etched prior to being rinsed with the alkaline solution to remove chromium oxide to further enhance the paint adhesion. Preferred rinsing times for the etchant, the alkaline solution and the silane solution are 2-5 seconds, 15-30 seconds and 5-10 seconds, respectively.

Metal pretreated with an inorganic/organic composite coating with

Painted metal sheet pretreated with an insoluble, composite layer containing siloxane. The composite layer is formed by rinsing the sheet with an alkaline solution containing at least 0.005M of a dissolved silicate or a dissolved aluminate, at least 0.1 vol.-% of an organofunctional silane and at least 0.02 vol.-% of a crosslinking-agent having two or more trialkoxysilyl groups. After the sheet is dried, the composite layer has a thickness of at least 10 .ANG.. After being painted, the siloxane forms a tenacious covalent bond between the paint and the metal substrate.

Metal pretreated with an aqueous solution containing a dissolved

Metal sheet protected against corrosion by a silane treated inorganic aluminate coating. A thin aluminate coating was formed by immersing a galvanized steel sheet into an alkaline solution containing 0.005M dissolved aluminate for about 30 seconds. The sheet was dried to form an adherent aluminate coating having a thickness of at least 50 .ANG.. The aluminate coated sheet was immersed into a solution containing 1.0 vol.-% hydrolyzed organofunctional silane for about 5 seconds forming a silane film having a thickness of at least 20 .ANG. on the outer surface of the aluminate coating. Thereafter, the silane treated aluminate coated sheet was painted. The silane film formed a covalent bond between the outer paint layer and the inner aluminate layer. A steel sheet treated with the silane sealed aluminate coating had good corrosion protection, good paint chipping resistance and good paint formability.

Metal sheet with enhanced corrosion resistance having a silane treated

A metallic coated steel such as a galvanized sheet is coated with a thin siloxane film having a preferred thickness of about 45 .ANG. for providing temporary corrosion protection. The siloxane film is formed by rinsing the metallic coated sheet with an aqueous solution containing 0.5-2.0 vol. % silane and 0.1-1.0 vol. % crosslinking agent. The silane coating deposited on the rinsed sheet is cured at a temperature less than 200.degree. C. Preferred silane and crosslinking agents are .gamma.-aminopropyltriethoxy and (CH.sub.3 O).sub.3 SiCH.sub.2 CH.sub.2 Si(OCH.sub.3).sub.3 respectively. The siloxane film may be removed by rinsing the metallic coated steel sheet in an alkaline solution prior to coating the sheet with a phosphate conversion coating and a paint.

Metallic coated steel having a siloxane film providing temporary

Steel sheet coated with a relatively insoluble, inorganic, corrosion resistant coating. A silicate coating is formed on a steel sheet by rinsing the sheet for at least 30 seconds in an alkaline aqueous solution containing 0.005 M silicate, 0.005 M metal salt and having a temperature of at least 25.degree. C. The sheet is dried to form an adherent silicate coating having a thickness of at least 2 nm prior to being treated with an aqueous solution containing 0.5-5 vol.-% silane. If the sheet is painted, the silane film forms an adherent bond between the paint and the silicate coating. A silane treated silicate coating minimizes red rusting on terne coated steel by sealing pin holes. A silane treated silicate coating also provides good corrosion protection and paint adherence on cold-rolled or galvanized steel.

Steel sheet with enhanced corrosion resistance having a silane treated

Steel sheet coated with a nontoxic, relatively insoluble, inorganic, corrosion resistant coating. A silicate coating is formed on a steel sheet by rinsing the sheet for at least 30 seconds in an alkaline aqueous solution containing 0.005 M silicate, 0.005 M metal salt and having a temperature of at least 25.degree. C. The sheet is dried to form an adherent silicate coating having a thickness of at least 2 nm prior to being treated with an aqueous solution containing 0.5-5 vol.-% silane. If the sheet is painted, the silane film forms an adherent bond between the paint and the silicate coating. A silane treated silicate coating minimizes red rusting on terne coated steel by sealing pin holes. A silane treated silicate coating also provides good corrosion protection and paint adherence on cold-rolled or galvanized steel.

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Middletown, OH, United States of America

Ashok Sabata