GB1562589A

GB1562589A - Electrotinning process and apparatus

Info

Publication number: GB1562589A
Application number: GB21192/78A
Authority: GB
Original assignee: USS Engineers and Consultants Inc
Current assignee: USS Engineers and Consultants Inc
Priority date: 1977-05-23
Filing date: 1978-05-22
Publication date: 1980-03-12
Also published as: TR20123A; AR218490A1; NO781761L; PL207041A1; JPS549127A; NL7805266A; BE867387A; FR2392142A1; IT7868170A0

Description

(54) ELECTROTINNING PROCESS AND APPARATUS (71) We, USS ENGINEERS AND CONSULTANTS INC., a corporation organized and existing under the laws of the State of Delaware, United States of America, of 600 Grant Street, Pittsburgh State of Pennsylvania, 15230, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to the electrotinning of ferrous substrates.

Past efforts to recover electroplating solution losses from commercial electrotinning lines have been very limited. One effort was to periodically manually remove accumulated sludge from plating tank. The sludge containing concentrated tin electroplating solution was then sold to a tin reclaimer.

Another effort was to remove water from rinse tanks which contain electroplating solution carried over from the plating tank by the plated substrate. The concentrated rinse solution was then returned to the plating tank. No attempt has been made to prevent the normal electroplating solution splashes, spills, and leaks from the operating tanks, pipe, valves, and pumps from escaping into the sewer. For example, in one operation these losses amount to an average loss of 0.3 gallon per minute. This seemly small quantity of plating solution contains approximately 33 pounds of tin and 171 pounds of phenolsulfonic acid in an eight-hour operat mg turn. Failure to collect these losses is costly because of loss of chemicals and leads to the necessity for expensive treatment facilities to treat these losses in sewagetreatment plants.

Additionally, when producing tin plated substrates grease would often build up in the electroplating solution resulting in defects in the form of spots on the final tinplate pro duct produced.

According to the present invention, there is provided an electrotinning process in which a cathodic ferrous substrate is passed through a bath of electroplating solution containing an acid electrolyte and tin ions, the process including removing electroplat ing solution from the plating bath, collecting spills of electroplating solution from the plating bath, filtering the removed solution and collected solution together and return ing the filtered solution to the plating bath.

The invention also provides an electrotinning apparatus comprising a plating tank, a rinse tank, a filter, means for conducting electrolyte from the plating tank to the filter, means for collecting spills from the plating tank and from the rinse tank and conducting the collected spills to the filter, a vacuum evaporator for evaporating the filtered solution, an indirect heat exchange condenser for condensing the gaseous fraction from the vacuum evaporator, means for returning the evaporated solution to the plating tank and means for returning the condensate from the condenser to the rinse tank.

The invention overcomes many of the prior art problems. There is a significant materials savings since tin and acid which formerly were discarded are now saved.

Secondly, the sources of pollution, that is, tin, acid and phenol present as an impurity in the acid, are eliminated and, therefore, costly antipollution equipment to clean up the waste waters are eliminated. Thirdly, the tinplate product is of better quality because of the elimination by filtration of greasy impurities which cause "spotting" of the tin coating.

The invention is further described, by way of example, with reference to the accompanying drawing which is a schematic representation of an electrotinning apparatus of the invention.

A ferrous substrate in the form of a strand of low carbon steel strip of any analysis suitable to the production of tinplate, which has been previously rolled to an intermediate gage, cleaned, pickled, and annealed is passed from an uncoiler 1 through a pre-plating treatment unit 2 including cleaning and/or pickling equipment, and then through a tin plating unit 3. The tin coated strip is then passed through rinsing and drying units 4 and 5 into a furnace 6 wherein the tin coating is reflowed and brightened. The strip leaves the furnace through a quenching tank 7 and passes to a drier 8. The tin coated strip then undergoes a protective treatment at station 9 including chemical treatment and oiling before being coiled at 10 for shipment or further use.A spill collector 11 collects electroplating solution spills from the in plating tank 3, rinse tank 4, and quenching tank 7 and directs the spills into holding tank 12 where the electroplating solution spills are held as desired prior to passing through the filter 13 which removes any greasy material and any other insoluble contaminants. Electroplating solution is also removed directly from the tin plating tank 3 and passed to circulating tank 14 prior to passage through filter 13. The filtered electroplating solution passes either back to circulating tank 14 for refiltering or to another circulating tank 15. Sludge 16 is removed from the filter 13 periodically as needed.

The electroplating solution in circulating tank 15 can either be sent back to the filer 13 or sent to the evaporator and condenser 17 for concentrating of the solution or may be sent back to one of the tanks containing electroplating solution such as tin plating tank 3 for reuse in the process. The concentrated electroplating solution from the evaporator can be sent to the circulating tank 15 and the condensate can be sent to a condensate holding tank 18 for reuse in the process.

In the evaporator and condenser 17, the solution is evaporated under vacuum. The vapor from the evaporator passes to an indirect heat exchange condenser, cooled by cold water.

WHAT WE CLAIM IS: 1. An electrotinning process in which a cathodic ferrous substrate is passed through a bath of electroplating solution containing an acid electrolyte and tin ions, the process including removing electroplating solution from the plating bath, collecting spills of electroplating solution from the plating bath, filtering the removed solution and collected solution together and returning the filtered solution to the plating bath.

2. A process as claimed in claim 1 in which the plated substrate is passed through a rinse bath and the step of collecting spills also includes collecting spills from the rinse bath, the process including vacuum evaporating the filtered solution and returning the evaporated solution to the plating bath.

3. A process as claimed in claim 2 in which the gaseous fraction from the vacuum evaporation is condensed by indirect heat exchange and the condensate is returned to the rinse bath.

4. An electrotinning apparatus comprising a plating tank, a rinse tank, a filter, means for conducting electrolyte from the plating tank to the filter, means for collecting spills from the plating tank and from the rinse tank and conducting the collected spills to the filter, a vacuum evaporator for evaporating the filtered solution, an indirect heat exchange condenser for condensing the gaseous fraction from the vacuum evaporator, means for returning the evaporated solution to the plating tank and means for returning the condensate from the condenser to the rinse tank.

5. An electrotinning process substantially as hereinbefore described with reference to the accompanying drawing.

6. An electrotinning apparatus substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. A ferrous substrate in the form of a strand of low carbon steel strip of any analysis suitable to the production of tinplate, which has been previously rolled to an intermediate gage, cleaned, pickled, and annealed is passed from an uncoiler 1 through a pre-plating treatment unit 2 including cleaning and/or pickling equipment, and then through a tin plating unit 3. The tin coated strip is then passed through rinsing and drying units 4 and 5 into a furnace 6 wherein the tin coating is reflowed and brightened. The strip leaves the furnace through a quenching tank 7 and passes to a drier 8. The tin coated strip then undergoes a protective treatment at station 9 including chemical treatment and oiling before being coiled at 10 for shipment or further use.A spill collector 11 collects electroplating solution spills from the in plating tank 3, rinse tank 4, and quenching tank 7 and directs the spills into holding tank 12 where the electroplating solution spills are held as desired prior to passing through the filter 13 which removes any greasy material and any other insoluble contaminants. Electroplating solution is also removed directly from the tin plating tank 3 and passed to circulating tank 14 prior to passage through filter 13. The filtered electroplating solution passes either back to circulating tank 14 for refiltering or to another circulating tank 15. Sludge 16 is removed from the filter 13 periodically as needed. The electroplating solution in circulating tank 15 can either be sent back to the filer 13 or sent to the evaporator and condenser 17 for concentrating of the solution or may be sent back to one of the tanks containing electroplating solution such as tin plating tank 3 for reuse in the process. The concentrated electroplating solution from the evaporator can be sent to the circulating tank 15 and the condensate can be sent to a condensate holding tank 18 for reuse in the process. In the evaporator and condenser 17, the solution is evaporated under vacuum. The vapor from the evaporator passes to an indirect heat exchange condenser, cooled by cold water. WHAT WE CLAIM IS:

1. An electrotinning process in which a cathodic ferrous substrate is passed through a bath of electroplating solution containing an acid electrolyte and tin ions, the process including removing electroplating solution from the plating bath, collecting spills of electroplating solution from the plating bath, filtering the removed solution and collected solution together and returning the filtered solution to the plating bath.