Lithographic printing plates of aluminum or aluminum alloys are provided with an anodized surface layer, to which a photosensitive layer may be directly applied, which displays excellent adhesion and durability in use. For this purpose, anodization is carried out with an aqueous solution containing a polybasic mineral acid such as sulfuric and a higher concentration of a polybasic aromatic sulfonic acid containing at least one additional nuclear acidic substituent, preferably two, selected from the group consisting of a carboxylic acid group and a phenolic hydroxyl group.
A process for electrolytically treating an article of aluminum or alloy thereof to form a glossy film thereon, the process comprising the step of subjecting the article to electrolysis in an aqueous alkaline bath containing sodium phosphate and at least one compound selected from the group consisting of organic acids, inorganic acids and salts thereof under the conditions of a bath temperature of 20.degree. to 90.degree. C. and a current density of 0.5 to 80 A/dm.sup.2.
Aluminum foil in the form of a continuous web for example, is anodically oxidized by first coating one side of the web with a material such as a polymeric material which is inert to the anodizing conditions and then electrolytically anodizing the uncoated side of the web. The laminate formed which can be used as a base plate for presensitized and wipe-on lithographic printing plates includes an aluminum foil coated on one side with an inert material and having an anodically oxidized layer on the other side which is formed after the one side is coated with the inert material.
According to the invention there is provided an electrochemical process for applying a firmly bonded insoluble metal oxide-organic complex on a metal surface by employing the metal as anode and a water-soluble poly basic organic acid as electrolyte together with a strong inorganic acid such as phosphoric acid or further admixed with another strong inorganic acid such as sulfuric. The polybasic acid may be a polyphosphonic acid, polyphosphoric and polycarboxyl acid, or polysulfonic acid and is advantageously polymeric. Polyvinyl phosphonic acid (PVPA) is a preferred electrolyte. Direct current is used. Pulsed plating may optionally be employed. The insoluble metal oxide-organic complex formed is composed of anodic oxide combined with polyacid, which forms a protective layer on the metal of improved corrosion resistance. The metal oxide-organic complex is well-suited to bond light sensitive coatings thereto. The metal may be steel or aluminum. The process is economical and the product novel.
A method of forming a highly-deflective surface on aluminum alloys. The, the composition comprising: cleaning a body formed from an aluminum alloy; electrobrightening the body; and desmutting the surface of the freshly-brightened body without etching. The bath comprises: 15-95 vol. % nitric acid and 1-85 vol. % acetic acid; 1-40 vol. % total water; and a source of fluoride ion supplying at least 35 grams per liter of fluoride. Ammonium bifluoride is the preferred source of fluoride.
The invention is directed to the electrochemical treatment of aluminum substrates in a non-aqueous solution of a polymeric polybasic organic acid to provide a surface complex which promotes the adhesion of subsequently applied coatings to said surface.
