Centro Sperimentale Metallurgico S.p.a.

Nuova Italsider S.p.a.

Italsider S.p.a.

Centaro Sviluppo Materiali S.p.a.

Nazzareno Azzerri

Massimo Memmi

Roberto Bruno

Leonardo Giorgi

Susanna Ramundo

Santa Alota

Alberto Tamba

Giovanni Milanese

The suitability of the kind of steel strip known as black plate, optionally coated with small quantities of tin or nickel for food packaging, is greatly improved by ensuring the presence of a layer of P-type semiconducting oxide on the surface thereof. The ratio of the number of Type-P charge bearing atoms (NA) of that semiconducting oxide to the numbr of Type-N charge bearing atoms (ND) is greater than 1.2. The quality of the plate is yet further improved by coating the oxide surface with a thin chromic passivation layer that also contains a P-type semiconducting oxide.

Steel strip for food packaging and process for production thereof

Electrolytic galvanizing process in which steel strip to be zinc coated is passed continuously through an acid electrolyte solution containing zinc ions and is used as a cathode, while the electrolyte solution is made to flow in the space between the cathode and the anode, in a cell having flat parallel electrodes. The plating current density and the fluid dynamic conditions of the electrolyte are related by the equation

Electrolytic galvanizing processes

The suitability of the kind of steel strip known as black plate, optionally coated with small quantities of tin or nickel for food packaging, is greating improved by ensuring the presence of a layer of P-type semiconducting oxide on the surface thereof. The quality of the plate is yet further improved by coating the oxide surface with a thin chromic passivation layer that also contains a P-type semiconducting oxide.

Steel strip for food packaging

A method according to the invention is based on the combination of the activation treatment of a steel object in an aqueous neutral solution with the use of auxiliary electrodes, dipped in the same activating solution, which causes the steel to be pre-plated.

Method for preplating steel surfaces

The adhesion of paint to steel sheets is improved by pretreating the steel sheets, prior to conventional annealing, surface finishing, oiling, degreasing, phosphating and painting operations, by connecting the steel sheet alternately as cathode and anode in an electrolytic cell containing a bath of 0.5 M-2 M sodium sulphate aqueous solution. The operating temperature is 20.degree.-100.degree. C., the pH is 6-8, the current density is 1 to 50 A/dm.sup.2, and the treatment time is 0.1-30 seconds, preferably 0.5-20 seconds, and most preferably about 5 seconds as cathode followed by about 5 seconds as anode.

Process for improving the adhesion of paint to steel sheets

The susceptibility of steel to electroplating is improved, by an electrolytic pretreatment of the steel part. The steel part is connected alternately as cathode and anode in an electrolytic cell containing an electrolytic bath which is an aqueous solution of sodium sulphate of a concentration from 0.5 M to 2.5 M and a pH of 6 to 8, at a temperature of 20.degree. to 100.degree. C. and a direct current density of 1 to 60 A/dm.sup.2.

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Pomezia, Italy

Nazzareno Azzerri