Note: Descriptions are shown in the official language in which they were submitted.
This invention relates to improvements in a water-
soluble film-forming rust preventive composition for use in
temporary protection of metal surfaces, particularly of iron
and steel products.
For the temporary rust prevention of such products
oil-film type anticorrosive materials are in wide use.
The oil-film types maintain the rust preventive
effect forrelatively long periods of time, but are known to have
shortcomings. For example, when their temporary coated films
are to be removed, they require (a~ degreasing and washing
with an alkali cleaner, solvent, etc., (b) an after~treatment
-of the waste liquor drained from the washing process, and (c)
;many man-hours and a high equipment cost for those purposes.
As attempts to overcome those shortcomings and provide
improvements, a water-soluble film-forming rust preventive
material and soft-film type water-soluble antirust composition
have already been proposed.
Their coated films continue to have the rust inhibitive
effect for long and can be simply removed by washing with water -
20 after they have fulfilled their purpose of temporary rust
prevention. With these advantages they have been applied to
land and marine tanks and other equipments and have successfully
rationalized the rust prevention andcontrol of those structures.
Still, the above-mentioned rust preventive material
and composition have problems yet to be solved which make
them practically useless for some types of tanks and apparatuses.
~;Among the problems in common are (i) lack of moisture
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resistance and consequent so-Ltening of the coated films in
summer or highly humid environmen-ts, (ii) necessity of hea-ting
and liquefying prior to coating the materials which are soft
solids at ordinary -temperature, and (iii) such high viscosity
upon melting that the materials require an airless spraying
machine or other special equipment for coating.
The present invention has been perfected with the view
to settling those problems and is directed to a water-soluble
film-forming rust preventive composition of great practical
value which is in the form of an appropriately viscous
liquid at ordinary temperature and applicable by a common air
spraying machine ~o form a coated film~ which film is highly
resistant to m~isture and capable of inhibiting rust for an
extended period of time and is readily removed~ after the
temporary use as such, by a treatment with water at ordinary
temperature.
According to the invention~ the water-soluble film-
forming rust preventive composition is prepared by modifying~
through mixing with an alkaline solution~ a homopolymer of
hydrocarbon having a double bond or bonds in the molecule
and selected from the group consisting of carboxylic acids
and anhydrides, and/or a copolymer of the said hydrocarbon
and an olefinic hydrocarbon having from 2 to 6 carbon atoms
per molecule.
The monomer, which may be regarded as an intermediate
product in the present invention, is either a homopolymer of
a monomer~ i.e.~ one of the hydrocarbons to be mentionecl
later~ or a copolymer of the hydrocarbon and an olefinic
hydrocarbon having from 2 to 6 carbon atoms per molecule~
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desir~bly with a polymerization degree between about 300 and
about 3000. If the polymerization degree is very low, the
rust preventive composition of the invention will have a
correspondingly low film-forming ability, and if the degree
is excessively high the composition will become so viscous
that it will pose problems in coatability as is the case with
the prior art compositions. Suitable hydrocarbons for use
as monomers in accordance with the invention are carboxylic
acids or anhydrides having double bonds in the molecules.
The numbers of such double bonds and carboxyl groups are not
critical7 but one or more each will be satisfactory. Examples
of such hydrocarbons include, but not limited to, acrylic
acid~ methacrylic acid~ cinnamic acid, maleic acid~
maleic anhydride, crotonic acidg allylacetic acid, allylpropionic -
acid, l-carboxy-l-ethyl ethylene, l-carboxy-l-propyl ethylene,
ethylacrylic acid, propylacrylic acid~ butylacrylic acid,
ethylmaleic acid~ and methylmaleic acid.
The olefinic hydrocarbon to form a copolymer with such
a carboxylic acid or anhydride is chosen from the hydrocarbons~
such as ethylen~ propylene~ butylene~ amyIene~ and hexylene~
having rom 2 to 6 carbon atoms in the molecule. An olefinic
hydrocarbon with 7 or more carbon atoms will not only impart
excessive viscosity to the resulting rust preventive composi-
tion but also have other undesirable effects upon the use o
the composition.
In synthesizing the homopolymer and copolymer rom the
hydrocarbons7 the usual polymerization reaction may be used.
In any case, the homopolymer, copolymer~ or their mixture
- thus obtained alone will not be able -to form a water-soluble
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rust preventive -film. The polymer or polymeric mixture will
be able to do so only when it is modified with a solution of
alkali, e.g., in water.
When the polymer is mixed in an aqueous solution or
the like of an alkali metal salt, e~g.~ sodium hydroxide, and
the mixture is treated by heating at a suitable temperature~
e.g.~ in the neighborhood of 70C~ the product will be a
~` viscous liquid at ordinary -temperature. This mixture will
work as a water-soluble film-forming rust preventive composi-
tion according to the invention.
Exactly what change the polymer does undergo upon the
modifying treatment is to be clarified yet~ but it is presumed
that at least a part or whole of the carboxyl groups in the
polymer produces a carboxylate.
The alkaline agent required for the modification is not
limited to the above-mentioned sodium hydroxide. Other alkali
metal salts9 such as lithium hydroxide and sodium carbonate,
alkali earbh metal salts~ such as magnesium oxalate3 calcium
hydroxide~ and barium carbonate, and ammonia may be used as
well. Aside from these inorganic alkaline agents, organic
ones, such as ethanolamine and hexylamine~ are useful) too.
The water-soluble film-forming rust preventive composi-
tion obtained in accordance with the invention occurs as a
viscous liquid at ordinary temperature which~ lmlike the
conventional compositions of the character, requires no pre-
heating to liquid form before application on metal surfaces
as of iron and steel products. It may be coated by ordinary
air sprayin~ machines as well as by airless spraying equipment~
to form fine resinous coated films on the metal surfaces.
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These resinous films are thin but capable of inhibiting
corrosion ~or long periods of time. Moreover, they are
moisture-proof as compared with the conventional coated
films, and have no possibility of softening in summer or
under high humidity conditions. On the contrary, they exhibit
a drying tendency and are able to isolate and protect
the metal surfaces from corrosive atmospheres. After having
served the purpose of temporary rust prevention, the coated
films can be easily removed from the metal surfaces by simple
immersion in or washing with water at ordinary temperature.
For added corrosion resistance, the water-soluble film~
- forming rust preventive composition of the invention may
contain a small percentage of a known rust inhibitor or inhi-
bitors.
The viscous mixture may thus contain one or more inhibi-tors
selected from among sodium nitrite7 sodium phosphate, sodium
borate, triethanolamine, dicyclohexylamine nitr~te~ and
petroleum sulfonate. Such a rust inhibitor, when mixed
in the composition and applied on a metal surface will be
secured thereto by molecular adsorption or will be passivated
thereon~ thus permitting the coated film to display an
e~cellent antirust effect for an extended period of time as
~ ~ compared with the film free of the inhibitor.
; The invention is illustrated by the following examples.Specimens (l), (2), and (3) of three embodiments of the
water-soluble film-forming rust preventive composition of the
invention were prepared in conformity with the compounding
recipe~ ~iven in the left column of Table 1. An exemplary
procedure for preparation is as follows. First~ a reaction
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vessel is filled with water, and potassium hydroxide and
magnesium hydroxide are charged into the vessel. The mixture
is heated to 70C~ and a maleic acid-butylene copolymer is
added, and all are thoroughly mixed. The mixture will then
become transparent or semitransparent. This is the specimen
(1). The specimen (2) may be prepared generally in accordance
with the above-described procedure. The specimen (3) was
obtained by adding sodium nitrite and trie-thanolamine to the
mixture o~' the specimen (~) when the latter became transparent
or semitransparent.
Table
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Speci- Compounding recipe of water- Qity Rust
men soluble ~ilm-forming rust coated develop
No. preventive composition (g/m2) ment
_
Maleic anhydride -
butylene copolymer lOOg
Potassium hydroxide 22 No
(1) ~agnesium hydroxide 25 5 rust
Water 9 _
Acrylic polymer lOOg
(2) Lithium hydroxide 7 40
Barium carbonate 30
Water 650
_ .
Maleic acid -
propylene copolymer lOOg
Sodium carbonate 30
(3) Calcium hydroxide30 40 ll . .
Sodium nitrite 30
Triethanolamine 40
Water 7
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Test I for corrosion preventive properties:
The specimens (1), (2), and (3) of water-soluble film-
forming rust preventive composition prepared in the manner
described were applied by air spraying machines on pieces of
soft polished steel sheet (SPC-C)~ 150 mm long, 70 mm wide,
and 3 mm thick~ and were dried -thereon. The test pieces
were suspended in outdoor shed-storage exposure testers for
corrosion test for 80 days. The testers were open to the
atmosphere but the test pieces therein were kept from rain
drops.
~- The results were as given in the rightmost column of
Table 1. The tes-t pieces coated with the specimens (1)~ (2),
` and (3) did not rust at all.
During the test period none of the coated films softened.
` 15 After the test the films came off completely from the metal
surfaces upon immersion in water at ordinary temperature for
about 10 minutes.
For comparison purposes, three different types of
; commercially available slushing compounds were used and tested
~ 20 for corrosion resistance in the same way as above described.
- As can be seen from Table 2 summarizing the results~ the test
pieces coated with specimens (4) and (5) rusted but the test
piece with a specimen (6) did not.
Following the test the coated films were removed from
the test pieces. ~or the removal -the films of the specimens
(4) and (5) requirecl about 20 minutes of immersion in a bath
of heated alkali degreaser and subsequent washing with water.
To remove the film of the specimen (6) the procedure just
; described had to be repeatecl twice.
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`Table 2
Speci- Type of Qlty Rust
men slushing compound coated develop-
(4) Slushing compound A 50g 20%
(5) Emulsion slushing 60 40%
compound rust
(6) Grease I 100 rust
Test II for corrosion preventive properties:
Specimens (1), (2), and (3j of three embodiments of
the water-soluble film-forming rust preventive composition
prepared from the ingredients shown in Table 1 were used to
form antirust films on condenser tube plates of a marine
power plant~ each measuring ~.2 meters by 5.0 meters.
Each tube plate was cleaned by a shot blast and one of
the specimens was applied by means o-f an airless spraying
machine on the metal surface to a film thickness of about 60
microns.
The plant cons-truction was carried out indoors but open
to the atmosphere, and welding and other associated operations
were performed around those tube plates. In brief~ the
environmsnt was more corrosive than those for ordinary tanks.
After the completion of fabrication and assembly of the
condenser (which had taken about three months), -the tube
plate surfaces were inspected. The -tube plates coated with
the specimens (1) and (2) showed slight, practically negligible
rust~ an~ the tube plats wi-th the specimen (3)had no -trace of
rust.
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The examples of the other useful compounding recipe
of composition in accordance with the present in~ention are
as follows.
(7) Maleic polymerlOOg
Magnesium carbonate 31g
Monoethanolamine8g
Water 650g
(8) Crotonic polymerlOOg
Barium hydroxide70g
Caustic potash 20g
Dicycrohexylammoniumnitri-te
20g
Triethanolamine 50g
:. Water 600g
(~ vaporizable corrosion inhibi.tor)
(9) Acrylic acid-propylene copolymer
lOOg
Calcium hydroxide 26g
Caustic potash lOg
Water 650g
(lO) Acrylic acid-isobutylene copolymer
lOOg
~ Magnesium carbonate 26g
: Caustic soda 6g
Borax 30g
Monoethanolamine40g
Water 600g .
As stated in detail above, the water-soluble film-
forming rust preverltive composition according to this in~ention
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is in liquid form with a suitable viscosity at ordinary
temperature for direc-t application to metal surfaces by an
air spraying machine. The resulting coated film is highly
moisture-resistant and has no possibility o-f so~tening in
S summer or in highly humid conditions. It proves rust pre-
ventive for a long period of time and, after having fulfilled
its purpose of temporary corrosion prevention, the film is
simply removed by immersion in or washing with water at
ordinary temperature. With these advantages the composition
-; 10 of the invention is extensively applicable to various tanks
and machineries~ marine or land, to provide temporary anti-
rust protection of great practical value.
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