US 4,231,851 AGranted

Method for electrochemically coating a metallic substrate with a protective film of a phenolic resin

AssigneesCentro Ricerche Fiat S.p.A., Consiglio Nazionale Delle Ricerche

InventorsGiuliano Mengoli, Sergio Daolio, Ugo Giulio, Carlo Folonari

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Abstract

Adherent insoluble coating film of a phenolic resin is obtained by electrolysis of an alkaline-reacting aqueous electrolyte comprising phenol, a mono- or di-substituted phenol with substituent(s) in o- or m-position, and an alkylene diamine, in specific proportions. The current density shall never exceed 10 mA/sq.cm. The voltage is from 2.5 V to 10 V and is preferably kept constant. Coating thickness values exceeding 1 micron and up to about 25-30 microns are obtainable within a short time at the expense of 2-2.5 Faradays per mole deposited phenol. The substituted phenol is preferably o-chloro-phenol, and the diamine is preferably ethylenediamine.

Claims9

Dependent claims

A method for electrochemically coating a metallic substrate utilized as anode in an electrochemical cell in which a direct current flow of electrical energy is passed from a cathode to said anode through a liquid alkaline-reacting electrolyte comprising at least one phenolic monomer and a basic substance dissolved in a normally liquid solvent, thereby to progressively form on said substrate an impervious adherent polymeric film of a phenolic resin, wherein the improvement comprises:

(a) the solvent is water, an alcohol having from 1 to 4 carbon atoms, or a mixture of the two;
(b) the phenolic monomer comprises phenol in an amount of from 50 to 250 g per liter electrolyte, and at least one halo-, alkoxy- or alkyl-substituted phenol in an overall amount of from 5 to 35 g per liter electrolyte, the substituent being in an ortho- or meta- position;
(c) the basic substance comprises an alkylene diamine in an amount of from 1 to 10 vol.% referred to the electrolyte;
(d) the direct current flow density does not exceed 10 mA/sq.cm. of the metallic substrate.

1 more element

Dependencies are inferred from the claim text.