Anti-corrosive three brothers of plating-substituting anticorrosive paint/natural resin rust prevention
paint/rust-converter agent
Minoru Sugiura
CEO, Sci-Paint Japan Inc.
Sci-Paint Japan Inc. has developed and marketed such specialized paints as inorganic paints,
water-based paints, and natural material paints.
When considering global environment, hazardous
influence of organic solvent are not only on our health but also on the natural society and global
environment.
In the painting industry until 60 to 70 years ago, few chemical materials were used except for
some special-purpose paints; usually, paint materials were produced from natural pigments and
natural resins. After World War 2, at around 1951, synthetic resins like melamine and epoxy resins
were developed in succession.
Usage of industrial products was widened in response to the post
war reconstruction and chemical synthesis technology was significantly improved, resulting in the
massive improvement of chemical paints in pursuance of economic efficiency such as cost and
workability.
On the other hand, what fell in victim were irretrievable assets like the environment and
people’s health.
In such circumstances, the problems of organic solvents have been highlighted and,
furthermore, there recently occur some unsolvable problems, in which the conventional chemical
paints cannot withstand, and, therefore, dissolved or deformed by the acid-rain caused by the air
pollution and the environmental pollution.
Based on these problems, Sci-Paint Japan Inc. has been studying and developing such paints
that are made from materials suitable to the period of the environment and have properties, also,
suitable to such period of the environment and that can reduce the problems concerning global
warming and exhaust of carbon dioxide; in other word, Sci-Paint Japan is developing the paints
specialized in the environmental features.
1.
Three brothers of anti-corrosive paints as environmentally-friendly paints
The first objective we dealt with is anti corrosive paints.
The rust is the challenge that we,
human beings, have been continuously struggling with since the dawn of the iron culture until now.
Since iron is the substance that is prepared by removing oxygen from the iron ore and being melted,
it is the natural providence that the iron reacts with oxygen to return to the original state.
How to
reduce the rate of this natural reaction has been the significant theme; therefore many methods like
anti corrosive oils and paints, metal plating, and galvanic protections, have been devised.
Especially, metal plating has been an effective measure because of its high anti corrosive capability,
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although it is a rather old technology used since old time.
However, such situations are going to be in the past tense.
The durability of the metal plating
is going to be lost because acid rain brought about by the industrial activities of people and air
pollution caused by automobile exhaust gas are giving significant influence on the plating surfaces.
Painting is also significantly affected by the acid rain; where, in combination with the
ultraviolet deterioration, acidic water containing chemical substances is penetrating through the
micro cracks and corroding iron by infiltrating into the metal surfaces through the interface with the
coating.
Though several new effective methods like metal spraying are devised, their costs are still
high and there are still problems about workability at site; accordingly, anti corrosion of iron in the
city construction structure has continuously been a serious problem.
Application of “KOUJIN”
(The result of durability test for 192 hours.)
Zinc plated test piece
(The result of 180 hour CASS test.)
Fig. 1
If the same good characteristics as those of metal plating and metal spraying are achieved in
paints, because being the simple and cost effective method, the paint method will achieve excellent
LCC in the construction work with the high environmental performance, where no carbon dioxide is
generated at the ambient temperature application; therefore we have started the development work
on this theme.
1.1 Inorganic silicone anti-corrosive paint, “KOUJIN”
This paint is the one in which a combination of fine zinc metal foils of micron-size and
acicular aluminum metal foils is kneaded with silicone resin.
It is a condensation hardening paint
with siloxane-linkage which utilizes the chemical reaction in which silicone reacts with
hydroxide-group of the iron material; and, because having electric conductivity and, therefore,
having sacrificial protection effect, it has similar characteristics of metal plating.
However, it is a
normal type paint of ambient temperature application without necessity of high temperature melting
like that for metal plating, and, therefore, considered to be an application-type substitute for metal
plating.
In the CASS test, which is for evaluation of metal plating, by Japan Paint Inspection and
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testing Association, it got the result of Ri2 (0.5 % of spot rust) in 192 hour durability test, whose
evaluation is equivalent to 40 year exposure.
test piece at 40 hour exposure.
In the same test field, rust occurred for a metal plated
Also, in a complex cycle test at an automobile manufacturer, it had
completed 1000 hour durability test.
Because being a surface coat with inorganic silicone and, therefore, strong for acid rain and
having strong durability against ultraviolet, we have developed KOUJIN as a heavy-duty
plating-substituting anti corrosive paint that can withstand such conditions by a thin film of 80 μ
thickness.
Fig. 2
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Fig. 3
Microgram of the cut plane of the coated surface
with “KOUJIN”
1.2 Natural resin rust prevention paints, “GILSO COAT”
Gilsonite was used in ancient Egypt before Christ in such usage as to preserve mummies and,
also, used in Europe as adhesives for stone structure buildings.
In Japan, it was used since old time
as water proof and antiseptic agents for wooden buildings.
However, the paints disappeared by the development of chemical paints about 50 years ago.
When watching old pictures, we often see black-colored bicycles and side cars. Also this paint was
used for chassis of automobiles both for water proof and anti corrosion.
We saw houses just after
World War 2 painted black, for which a paint prepared by purifying the natural resin Gilsonite
(asphalt) was painted.
This paint was used as a versatile paint for water proof and anti corrosion at that time of no
chemical paints.
This paint of strong water proof and anti corrosive performance, and of high
adhesive property is prepared by purifying the mixture of natural tar and linseed oil or wood oil.
We have redeveloped this technology once disappeared 50 years ago; which, we believe, is a natural
resin paint suitable for the environmental problems of today in the areas of anti corrosive application
for reinforcing steel of PC, and anti corrosive maintenance operation for train bridges, because it is
effective by a simple way of application.
1.3 Rust-converter type anti-corrosive paint, “MAGNE COAT”
In any anti-corrosive work, surface preparation work (keren work) is a must.
But there are
many problems concerning the rust like time and hazard necessary for the surface preparation work
(keren work) and problems to the environment; we have developed this paint in response to the
requirement for the paints that need no surface preparation work.
In addition to the requirement of
no surface preparation, there are a few other difficult requirements like to be moderate in price and
economically superior, for their field work to be short in time, and to maintain long-time durability;
which have been solved by the use of this rust converting agent.
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“MAGNE COAT” is a coating
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agent that forms a cross-linked film by reacting acrylic emulsion resin with a special solvent.
Iron
will form red rust by oxidation, and, if the oxidation progresses, it is impossible to prevent corrosion
of iron without the surface preparation work (keren) that removes oxidation film of red rust.
If this
red rust is converted to the black rust, further oxidation of iron can be prevented.
Black rust has such tight surface structure that it prevents the penetration of hydroxides like
water.
Into “MAGNE COAT”, special tannic acid is added.
Tannic acid has so strong a reducing
power that it changes red rust (Fe2O3) into black rust (Fe3O4).
It is a series of water-soluble
compounds that reacts with metal to form hardly-soluble salts, which forms tight passive-state film
on the iron surface to prevent water penetration by deforming red rust into black rust.
The paint is used as a primer which should be applied on the surface at the proper timing.
2. Aiming to achieve long-lasting anti-corrosive performance
Using properly these three kinds of paints according to the environment and situations of the
work sites, and rust conditions is supposed to be effective to prevent variety of rust in steel-structure
and construction.
Such a perpetual problem like rust cannot be solved without selecting proper
measures depending on the site conditions and considering the specific characteristics of the rust.
In the case of giving heavy importance to LCC concept for long-time anti-corrosion, it is
effective to use the plating-substituting paint “KOUJIN” that is prepared from the substrate to have
an electric conductivity.
“KOUJIN” is also effective to repair metal plating.
Sci-Paint Japan Inc. is grappling with carbon offset.
In metal plating, an enormous quantity
of carbon dioxide is always generated because metal plating requires melting zinc and aluminum at
700°C at the processing stage.
Also, metal plating requires high cost to transport steel and iron
materials to and from the plating factory, which generates a large quantity of carbon dioxide.
On
the other hand, “KOUJIN” consumes no heat energy because it is applied at the ambient temperature
at site.
In addition, “KOUJIN” will not deteriorate iron’s durability and tensile force because there
are neither heat brittle fatigues at metal plating nor problems of hydrogen brittleness.
2Fe → 2Fe2+ + 4eIron is ionized and dissolved into water.
Zinc ion
Oxide film
2Fe2O + O2 + 4e- → 4OHElectrons emitted from the iron mediate the
reaction between water and oxygen to form
hydroxide ion.
2Fe2+ + 4OH- → 2Fe(OH)2
Iron ions and hydroxide ions react with each
other to form iron hydroxide (rust).
Fig. 4
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Iron
Mechanism of sacrificial anode action
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“MAGNE COAT” is a paint that converts red rust without going through the surface
preparation work (keren) that requires power consumption and blasting work; resulting in the
substantial reduction of work procedures and energy consumption.
“GILSO COAT” compounds linseed oil and wood oil into other natural material without any
chemical processing, resulting in maintaining the safe environment and effective anti corrosion
effect with low price materials.
We are now challenging the new technologies to maintain the environment and to aim carbon
offset.
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