Abstract: A method is described for maintaining constant chemical composition in solutions used for wet chemical processing. All chemical species that are deliberately included in the bath are kept at constant concentration primarily by a method of compensating for their depletion or generation with a set of feed solutions that are formulated and dosed into the bath in accordance with an overall material balance. Further, all chemical species not deliberately included in the bath are kept at constant concentration primarily by keeping the aggregate volume of replenishing stocks in strict proportion to the process service performed by the bath (e.g. the charge passed in an electroplating cell). Finally, a time-based scheme completes the control of the concentration of all bath species by controlling any species (whether deliberately included in the bath or not) that is depleted or generated as the result of chemical reactions which occur independently and/or spontaneously with time.

Abstract: Stannous electrolytic tinplating baths utilized in flat-rolled steel tinplating operations contain non-filterable lead in solution at undesirable levels because of the lead content of commercially available tin anode materials. As taught herein, lead in the electrolyte is controllably incapacitated for deposition with the tin by chemical treatment of the bath which establishes, in solid phase, an insoluble bivalent metal compound having an affinity for lead which is adsorbed. In a preferred halogen-system embodiment, calcium fluoride presents an extended surface area for adhesion of lead and not only incapacitates lead in the bath for deposition purposes but also enables separation of such adsorbed lead from the plating bath as part of sludge removal.

Abstract: A method for plating tin onto the surface of steel strip in an acidic electrolyte bath utilizing insoluble anodes is disclosed. Free acid in the bath is extracted from the bath and concentrated. Tin is dissolved in the concentrated extract and the extract is returned to the bath to replenish the tin in the bath.

Abstract: A system is provided for regenerating reducing agents used in ancillary chemical or electrochemical processes such as restoring solderability of electronic components. The system includes a cathode, an anode, and an electrolyte system that is separated by a semipermeable ionic barrier into a catholyte and an anolyte. The catholyte includes the reduced member of a redox couple, which can be regenerated electrochemically. The redox couple of the electrolyte system is charged like a battery and discharged during the ancillary process. Regeneration of the reduced member of the redox couple is accomplished at the cathode. The cathode comprises an electrode having a high hydrogen overvoltage so that sufficiently negative potentials can be attained while minimizing hydrogen evolution. Chemical balance is maintained by the semipermeable ionic barrier, which permits proton migration from the anolyte to the catholyte but acts as a barrier against diffusion and migration of cations from the catholyte to the anolyte.

Abstract: A process and apparatus for regenerating a plating bath comprising trivalent chromium cations (a trivalent chromium bath). The bath can be continuously, or more preferably, periodically with an ion exchange resin, preferably a cation exchange resin. A useful apparatus comprises a plating tank containing a trivalent chromium plating bath in communication with an ion exchange bed continuing ion exchange resin.

Abstract: For replenishing a metal ion to a plating bath, a soluble electrode of the same type of metal as in the bath and a counter electrode of a metal material having a nobler standard electrode potential than the soluble electrode are immersed in the bath. Electricity is conducted between the soluble electrode and the counter electrode, thereby dissolving the soluble electrode to replenish an ion of the metal of the soluble electrode to the bath. The potential of the counter electrode is measured using a reference electrode of the same metal as the soluble electrode. The quantity of electricity is controlled such that the measured potential may not be negative with respect to the reference electrode, thereby preventing deposition of the dissolving metal ion on the counter electrode while ensuring a high rate of metal ion dissolution.

Abstract: The total organic content (TOC) of an aqueous composition is reduced to 200 ppm or less by subjecting the composition to electrolysis whereby the pH of the composition at the start of the electrolysis is about 1.8 to about 7 to thereby electrolytically decompose organic materials contained in the aqueous composition.

Abstract: A stabilized spray displacement tin plating process of copper printed circuit innerlayers is disclosed for the manufacture of multilayer printed circuit boards. During prolonged use of spray tin plating, the plating solution becomes saturated with cupurous thiourea complex which precipitates interfering with spray nozzles and other mechanical components. The tin plating solution is stabilized by removing portions from the reservoir before saturation is reached, selectively precipitating the thiourea complex, and returning the remaining solution back to the reservoir. The precipitated cupurous thiourea complex is redissolved in acid and either disposed of by conventional waste treatment or the acid solution can be electrowinned to reclaim copper and oxidize thiourea to form a more acceptable acid solution for waste treatment.

Abstract: An electroplating cell having soluble and insoluble anodes is provided with a primary power supply having a positive terminal connected to the soluble anodes and a negative terminal connected to a cathode including workpieces to be plated. An auxiliary power supply has a positive terminal connected to the insoluble anodes and a negative terminal connected to the negative terminal of the primary power supply so that the voltage applied to the insoluble anode is equal to the sum of the voltages applied by the two power supplies.

Abstract: Iron foil is made by deposition of iron in an electrochemical cell having an insoluble anode from an acid electrolyte onto a moving cathode by the reaction:Fe.sup.2+ +2e.sup.- .fwdarw.Fe (foil) (I),and removing the iron foil so made from the cathode. In a regenerator iron is dissolved into the electrolyte. To avoid reduction of the foil by Fe.sup.3+ in the electrolyte, hydrogen in the form of hydrogen gas or a gas containing hydrogen is supplied to the anode, the anode being such that the anode reaction:H.sub.2 .fwdarw.2H.sup.+ +2e.sup.- (II)takes place, said reaction (II) predominating at the anode over the reaction:2Fe.sup.2+ .fwdarw.2Fe.sup.3+ +2e.sup.- (IV).The dissolution of iron in the regenerator takes place at least partly by the reaction:Fe+2H.sup.+ .fwdarw.Fe.sup.2+ +H.sub.2 (III).

Abstract: A process and apparatus for electroplating metals in which the metal salt concentration within the electroplating bath is reduced by providing an insoluble anode assembly in the bath. The insoluble anode assembly includes an enclosure which defines a compartment around an insoluble anode and which is formed at least in part by an anion exchange membrane. The primary reaction at the insoluble anode during electroplating is electrolysis of water to produce predominantly oxygen and hydrogen ions. The flow of current through the insoluble anode assembly causes anions in the plating solution to travel through the anion membrane into the compartment, resulting in an increase in acid concentration within the compartment. Accumulated acid is periodically flushed from the compartment.