An Insulating Medium for Protecting Iron and Steel Ships' Plates, and other Submerged Surfaces of Iron and Steel
Year: 1885

page_text: An Insulating Medium for Protecting Iron and Steel Ships'
Plates, and other Submerged Surfaces of Iron and Steel, from
I, JAMES BLENKINSOP, of the Blue House, Albrighton in the County of Salop,
barrister-at-law, do hereby declare the nature of this invention to be as follows:-
It is well known that certain metals and chemicals, such as copper and copper
preparations, when such are employed in anti-fouling compositions, are liable to
corrode the iron or steel plates or sheets, or other submerged surfaces of iron or
steel, coated with such compositions.
Now, the object of this invention is to provide an insulating medium between
such anti-fouling compositions and the iron or steel surfaces which they are
employed to protect.
According to this invention, I form a suitable varnish or composition, containing,
as the insulating agent, zinc in a finely divided state, commercial zinc dust being
very suitable for the purpose. The varnish or composition thus formed is laid over
the surface to be protected previously to the anti-fouling composition being laid
thereon.
The proportionate quantity of zinc in the varnish or composition may vary
considerably, but it is advisable not to have less than the amount of metallic copper,
or other corrosive material which is present in the anti-fouling composition.
STEPHEN WATKINS,
Agent for the Applicant.

page_text: I, JAMES BLENKINSOP, formerly of the Blue House, Albrighton in the County of
Salop, but now of Egham in the County of Surrey, barrister-at-law 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:-
It is well known that certain metals and chemicals, such as copper and copper
preparations, when such are employed in anti-fouling compositions, are liable to
corrode (by electro-galvanic action) the iron or steel plates or sheets, or other
submerged surfaces of iron or steel, coated with such compositions.
Now, the object of this invention is to provide an insulating medium between
such anti-fouling compositions and the iron or steel surfaces which they are
employed to protect.
According to this invention, I form a composition containing, as the insulating
agent, zinc in a finely divided state, commercial zinc dust being very suitable for
the purpose. The composition thus formed is laid on, as in painting, over the
surface to be protected previously to the anti-fouling composition being laid
thereon.
A varnish is employed as the vehicle for the zinc, and may consist of any quick-
drying varnish usually employed under water, such for instance as Resin Spirit
varnish, one gallon of the varnish being used to three pounds of zinc dust, and
one and a half pounds of oxide of zinc being added to such mixture to give body
to the composition.
The composition, however, which I prefer to employ is prepared as follows:-
A varnish is first made by dissolving (liquefying) one hundredweight of resin of
good quality (amber resin being preferred) in a copper, by heat, and when the
resin has become dissolved (liquefied) the source of heat is cut off, or the copper
removed therefrom, to allow the resin to cool, and when sufficiently cool, say
when at about a temperature of 200 degrees Farenheit, there are added, cold,
eight gallons of pure coal tar naptha and also one gallon each of the best pine
varnish and thrice-boiled linseed oil. Three pounds of zinc dust, and one and a
half pounds of oxide of zinc, to give body, are ground in a paint mill with half a
gallon of the varnish made as described in this paragraph, when cold, and afterwards
the varnish and also pure coal tar naptha are added cold to make up one gallon of
composition containing the insulating agent. The coal tar naptha is added to give
to the composition the consistency of ordinary paint and the quantity necessary to
be thus added varies somewhat with the atmospheric temperature, usually about
half a pint is added in making up one gallon of the insulating composition.

page_text: The composition above described may be varied considerably in its proportions
and ingredients; the essential feature of the invention being the employment of
the zinc in a finely divided state as the insulating medium for the purpose described;
but the composition described in detail may be employed for general application
for the purpose of providing an insulating medium between anti-fouling com-
positions of the character described and the submerged surfaces of iron or steel
coated therewith.
The oxide of zinc is employed simply to give body to the composition, and not
as of itself an insulating agent.
One coat of the composition will usually be found sufficient, but two or more
coats may be laid on if desired.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is :-
1. An insulating medium containing as an essential zinc in a finely divided state
for employment between anti-fouling compositions of the character described and
the submerged iron or steel surfaces which they are employed to protect, substan-
tially as described and for the purpose set forth.
2. A composition consisting essentially of zinc in a finely divided state with a
quick-drying varnish capable of employment under water, substantially as described
and for the purpose set forth.