Improvements in or relating to the Tinning of Articles made of Cast Iron.
Year: 1893

page_text: Date of Application, 2nd Feb., 1898
Complete Specification Left. 30th Oct., 1893-Accepted, 2nd Dec., 1893
PROVISIONAL SPECIFICATION.
Improvements in or relating to the Tinning of Articles made of
Cast Iron.
A communication from Messrs. WOLF, NETTER, and JACOBI, of 66, Lindenstrasso,
Berlin, in the Kingdom of Prussia.
I, ALFRED JULIUS BOULT of 323 High Holborn, in the County of Middlesex,
M.I. Mech. E. and Chartered Patent Agent, do hereby declare the nature of this
invention to be as follows:-
This invention relates to a process for tinning uniformly and brightly articles
made of cast-iron without previous decarbonization by immersing same into
molten tin.
The tinning of crude cast-iron has hitherto offered great difficulties and has been
very expensive as it has always boen necessary to anneal it previously.
For this purpose the article mado of cast iron was packed in cementing
powder, into oxygen containing substances such as red iron ore, magnetic
iron, manganese ore etc., and thon highly heated without admission of air for a
considerable time in a hermetically closed receptacle. By this means a partial
decarbonization of the crude cast iron was obtained, and the latter was then
capable of being tinned fairly well, but never completely satisfactorily. So many
difficulties however are adherent to this method especially when articles of large
dimensions are to be treated, that tinning became too expensive and impracticable.
In a recently discovered process by which an electro-coating of pure iron is
produced, it has been attempted to remedy these defects, but this process like-
wise offers many difficulties which will be obviated by the hereinafter described
process.
My correspondents new process consists essentially in providing the articles made
of cast iron with an electro-coating of an alloy of iron and nickel or of iron and
cobalt respectively. To such a coating tin readily adheres.
The solution for producing such alloys is preferably prepared from the following
chemical substances. A mixture consisting of 1 kilogram of sulphate, nitrate
or hydro-chlorate of nickel, 3 kilograms of ferrous sulphate and 1 kilogram of
citric or tartaric acid, or a mixture consisting of kilogram of sulphate, nitrate
or hydrochlorate of cobalt, 3 kilograms of ferrous sulphate and 1 kilogram of
citric or tartaric acid is entirely dissolved in 100 litres of water, to which solution
is then added a sufficiently large quantity of alkaline carbonate or of caustic
alkali for neutralizing it completely; the conductibility of this solution may be
increased by adding about half a kilogram of bisulphite of potash, soda or
ammonia. Into this solution the carefully scoured articles made of cast iron are
suspended as kathodes the anodes being composed of iron-nickel or cobalt-sheet,
the dimension of which must correspond to that of the kathode, whereupon the
electric current is allowed to act. For producing a deposit of this alloy of iron
and cobalt or of iron and nickol respectively upon cast iron the intensity of the
current should be about 50 amperes, at a potential at the terminals of 7 volta
per 1 square meter of surface of the articles to be treated. By electro-chemical
decomposition a white-grey coating of ferro-nickel or of ferro-cobalt is very rapidly
deposited; this coating adheres very firmly to the cast iron, it is very compact and
its hardness is like that of steel.
That the electro-coating consists really of an alloy of iron and nickel or of iron
Bud cobalt, has been proved by chemical analysis giving as result nearly 95% of
iron and about 3% of cobalt or nearly 94% of iron and about 4% of nickel
respectively. This coating of iron and nickel or of iron and cobalt respectively

page_text: is much more uniform than would be the case if the solution contained merely
iron, in which case the galvanio deposit consists of pure iron. By means of this
new solution which in addition to iron salts contains also nickel- or cobalt-salta
respectively, cast-iron articles formed in relief may be coated in a uniform mannor,
which without this addition, would not be possible, as only the raised portions would
be covered with a regular deposit of iron, and not the recessed ones, and molten tin
would therefore not adhere when the article was immersed which would render the
finished product valueless.
.
After the article of cast iron has entirely and uniformly been provided with this
coating, it is first dipped into soldering water consisting of chloride of zinc and
then into a bath of molten tin, the surface of which is covered in order to prevent
'oxidation, with chloride of zinc or with fat. In order to maintain the above described
liquid in a constant condition it is necessary to make up from time to time the
compounds contained therein; ferrous sulphate, nickel- or cobalt salt respectively,
and acid, such as tartaric citric, oxalic, acetic, formic, or sulphuric acid are then
added to the solution.
It will be understood that my correspondents do not confine themselves to the
precise chemicals or the proportions above specified, as obvious modifications may
be made without departing from the spirit of the invention.
Dated this 2nd day of February 1893.
W. P. THOMPSON & BOULT,
London, Liverpool, Nottingham, and Manchester, Agents for the Applicants.
.
.
COMPLETE SPECIFICATION.
Improvements in or relating to the Tinning of Articles made of
Cast Iron.
A cominunication from Mossrs. WOLF, NETTER, AND JACOBI, of 66, Lindenstrasse,
Berlin, in the Kingdom of Prussia.
1, ALFRED JULIUS BOULT of 323 High Holborn in the County of Middlesex,
Chartered Patent Agent, do hereby declare the nature of this invention and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement :-
This invention relates to a process for tinning uniformly and brightly articles
made of cast-iron without previous decarbonization by immersing samo into molten
tin. The tiuning of crude cast-iron has hitherto offerod great difficulties and has
been very expensive as it has always been necessary to anncal it previously.
For this purpose the article made of cast iron was packed in cementing powder, i.e.,
into oxygen containing substances such as red iron ore, magnetic iron, manganese
ore etc., and then highly heated without admission of air for a considerable timo in
a hermetically closed receptacle. By this means a partial decarbonization of the
crude cast iron was obtained, and the latter was then capable of being tinned
fairly well, but never completely satisfactorily. So many difficulties however are
adherent to this method especially when articles of large dimensions are to be
treated, that tinning became too expensive and impracticable. In a recently
discovered process by which an electro-coating of pure iron is produced; it has
been attempted to remedy these defects, but this process likewise offers many
difficulties which will be obviated by the hereinafter described process.
My correspondents' new process consists essentially in providing the articles made
of cast iron with an electro-coating of an alloy of iron and nickel or of iron and
cobalt respectively. To such a coating tin readily adheres.
The solution for producing such alloys is preferably prepared from the following
chemical substances. A mixture consisting of 1 kilogram of sulphate, nitrate or
hydrochlorate of nickel, 3 kilograms of ferrous sulphate and 1 kilogram of citric or
tartaric acid, or a mixture consisting of kilogram of sulphate, nitrate or hydro-
chlorate of cobalt, 3 kilograms of ferrous sulphate and 1 kilogram of oitric or tartaric

page_text: acid is entirely dissolved in 100 litres of water, to which solution is then added a
sufficiently large quantity of alkaline carbonate or of caustic alkali for neutralizing
it completely; the conductibility of this solution may be increased by adding about
half a kilogram of bisulphite of potash, soda or ammonia. Into this solution the
5 carefully scoured articles made of cast iron are suspended as kathodes the anodes
being composed of iron-nickel or cobalt-sheet, the dimension of which must corre-
spond to that of the kathode, whereupon the electric current is allowed to act.
For producing a deposit of this alloy of iron and cobalt or of iron and nickel respec-
tively upon cast iron the intensity of the current should be about 50 amperos, at a
▸ potential at the terminals of 7 volts per 1 square meter of surface of the articles to
be treated. By electro-chemical decompositiou a white-grey coating of ferro-nickel
or of ferro-cobalt is very rapidly deposited; this coating adheres very firmly to the
cast iron, it is very compact and its hardness is like that of steel.
That the electro-coating consists really of an alloy of iron and nickel or of iron
and cobalt, has been proved by chemical analysis giving as result nearly 95% of
iron and about 3% of cobalt or nearly 94% of iron and about 4% of niokel
respectively. This coating of iron and nickel or of iron and cobalt respectively is
much more uniform than would be the case if the solution contained merely iron,
in which case the galvanic deposit consists of pure iron. By means of this new
solution which in addition to iron salts contains also nickel-or cobalt-salts
respectively, cast-iron articles formed in relief may be coated in a uniform mauner,
which without this addition, would not be possible, as only the raised portions
would be covered with a regular deposit of iron, and not the recessed ones, and
molten tin would therefore not adhero when the article was immersed which would
render the finished product valueless.
After the article of cast iron bas entirely and uniformly been provided with this
coating, it is first dipped into soldering water consisting of chloride of zinc and then
into a bath of molten tin, the surface of which is covered in order to prevent
oxidation, with chloride of zinc or with fat. In order to maintain the above
described liquid in a constant condition it is necessary to make up from time to
time the compounds contained therein; ferrous sulphate, nickel-or cobalt salt
respectively, and acid, such as tartaric, citric, oxalic, acetic; formic, or sulphurio
acid are then added to the solution.
It will be understood that my correspondents do not confine themselves to the
precise chemicals or the proportions above specified, as obvious modifications may
be made without departing from the spirit of the invention.
Having now particularly described and ascertained the nature of the said inveu-
tion as communicated to me by my foreign correspondents, and in what manner the
same is to be performed, I declare that what I claim is :-
1. A process for tinning articles made of cast-iron consisting in coating them
prior to their immersion into a bath of molten tin with an electro-deposit of an
alloy of iron and nickel or of iron and cobalt respectively the solution of metallic
salts for producing such alloys consisting of sulphate nitrate or hydrochlorate of
cobalt or nickel in combination with ferrous sulphate and citric or tartaric acid
and neutralized by means of an alkaline carbonate or caustic alkali; the conduc-
tibility of the solution being increased by the addition of bisulphite of soda potash
or ammonia substantially as set forth.
2. The application of an acid such as citric tartaric oxalio acetic formio or
sulphuric acid in order to maintain the solution characterized in the first claim in a
constant condition, substantially as set forth.
Dated this 20. 1.-ham 1802
W. P. THOMPSON & BOULT,
London, Nottingham, Liverpool, and Manchester, Agents for the Applicants.