A multi-layer surface-treated steel plate comprises a zinc-containing plated layer, a lithium silicate film layer formed on said plated layer and an organic composite silicate film layer composed of colloidal silica and an organic resin, which is formed on the lithium silicate film layer.

BACKGROUND OF THE INVENTION 
(1) Field of the Invention 
The present invention relates to a multi-layer surface-treated steel plate 
having a zinc-containing layer, and the present invention provides a 
surface-treated steel plate excellent in the rust proofness, paint 
adhesion and corrosion resistance of the coating. 
(2) Description of the Prior Art 
As the surface-treated steel plate to be employed as a substrate to be 
coated in the field of production of household electric appliances or 
construction materials, there have broadly been used products obtained by 
forming a phosphate treatment layer or chromate treatment layer on a 
zinc-deposited steel plate. In a chromate-treated zinc-deposited steel 
plate, a good corrosion resistance can be obtained owing to the 
passivating action of chromium, but there are problems concerning the 
toxicity of chromium and the waste water treatment. The phosphate 
treatment provides an undercoating having excellent properties, but in 
order to obtain a sufficient corrosion resistance, the chromic acid 
treatment should be performed as the post treatment and because of this 
post treatment, the same problems as encountered in the chromate treatment 
arise and furthermore, a problem of disposal of sludges formed in large 
quantities arises. Moreover, surface-treated steel plates obtained by 
either the chromate treatment or the phosphate treatment are still 
insufficient as substrates to be coated in the corrosion resistance of the 
coating, the paint adhesion and the degreasing resistance. Accordingly, 
development of a surface-treated steel plate having excellent, 
well-balanced properties as a substrate to be coated has been desired in 
the art. 
As the surface-treatment method for solving the foregoing problems, there 
has been proposed a method using a silicate composite composed of silica 
and an acrylic copolymer (see Japanese Patent Publication No. 34406/79), 
and some improvements of this methods have been proposed in Japanese 
Patent Application Laid-Open Specifications No. 77635/79 and No. 62971/80. 
However, when this silicate composite (hereinafter referred to as "organic 
composite silicate") is applied to a zinc-deposited or zinc 
alloy-deposited steel plate, the paint adhesion is improved over the paint 
adhesion attained by the existent chromate treatment or phosphate 
treatment, but the corrosion resistance in either the uncoated state or 
the coated state is insufficient and it is desired to further improve the 
corrosion resistance. 
SUMMARY OF THE INVENTION 
It is a primary object of the present invention to provide a multi-layer 
surface-treated steel plate in which the foregoing problems involved in 
the conventional techniques can effectively be solved. 
More specifically, in accordance with the present invention, there is 
provided a multi-layer surface-treated steel plate comprising a 
zinc-containing plating layer, a lithium silicate film layer formed on 
said plating layer and an organic composite silicate film layer composed 
of colloidal silica and an organic resin, which is formed on the lithium 
silicate film layer. 
DETAILED DESCRIPTION OF THE INVENTION 
The multi-layer surface-treated steel plate of the present invention 
comprises as a substrate a zinc-deposited steel plate or a zinc 
alloy-deposited steel plate and is characterized in that a lithium 
silicate [Li.sub.2 O.nSiO.sub.2 in which n is a number of from 2 to 20] 
film layer is formed on the surface of the zinc-containing layer of the 
substrate and an organic composite silicate film layer obtained by 
reacting and coupling colloidal silica with an organic resin is formed on 
the lithium silicate film layer. 
In the organic composite silicate film formed from colloidal silica and an 
organic resin, the organic resin component has mainly an effect of 
improving the paint adhesion while the silicate component (colloidal 
silica) has an effect of improving the corrosion resistance. However, in 
the case where this organic composite silicate film alone is applied, the 
corrosion resistance in either the uncoated state or the coated state is 
inferior. The reason is considered to be as follows. 
In the case where the silicate component in the organic composite silicate 
film forms a dense film on the entire surface of the plating layer, 
dissolution of the zinc plating film is controlled and an excellent 
corrosion resistance can be attained. Practically, however, areas not 
covered with the silicate are locally formed on the surface of the plating 
layer, resulting in reduction of the corrosion resistance. Accordingly, in 
order to improve the corrosion resistance of the organic composite 
silicate film, a dense silicate film is formed as a first layer and an 
organic composite silicate film is formed as a second layer on the first 
layer. The present invention has been completed based on the results of 
our researches made on this two-film-layer structure. 
The lithium silicate film as the first layer can be formed by coating an 
aqueous solution of lithium silicate [Li.sub.2 O.nSiO.sub.2 in which n is 
a number of from 2 to 20], drying the coating, washing the coating and 
drying the coating again. As the film-forming silicate, there can be 
mentioned not only lithium silicate but also alkaline silicates such as 
sodium silicate, potassium silicate and amine silicate, and sol-like 
colloidal silica. However, silicates other than lithium silicate have no 
substantial effect. In case of an alkaline silicate other than lithium 
silicate, the alkaline component left on the surface of the silicate film 
inhibits bonding of the silicate film to the organic composite silicate 
film. On the other hand, in case of lithium silicate, since the alkaline 
component left on the surface is sufficiently removed by water washing, a 
good adhesion is attained between the silicate film and the organic 
composite silicate film. It is considered that this is the reason why a 
steel plate substrate having excellent properties can be obtained. When 
colloidal silica is used for the silicate film of the first layer, there 
is obtained no effect. It is construed that the reason is that since 
colloidal silica is composed of particles, the formed film is a porous 
film having many defects and hence, the corrosion resistance of the 
organic composite silicate film cannot be improved by this porous film. 
The lithium silicate film will now be described. 
The molar ratio n in lithium silicate Li.sub.2 O.nSiO.sub.2 is preferably 
in the range of from 2 to 20, and if the molar ratio is 4 or higher, the 
boiling water resistance and corrosion resistance of the coating tend to 
increase. If the molar ratio n is lower than 2, the alkaline component 
(Li.sup.+) is left on the surface of the lithium silicate film, and if the 
molar ratio n is higher than 20, the properties of the lithium silicate 
film become similar to those of the colloidal silica film. Accordingly, no 
good results can be obtained unless the molar ratio n is in the range of 
from 2 to 20. 
The amount of the lithium silicate film deposited on one surface (as 
calculated as SiO.sub.2) is ordinarily in the range of 0.001 to 1 
g/m.sup.2, preferably 0.01 to 0.5 g/m.sup.2. If this amount is smaller 
than 0.001 g/m.sup.2, no substantial effect can be attained, and if the 
amount is larger than 1 g/m.sup.2, since the processability of the 
silicate film is inferior, no good undercoating can be obtained because of 
reduction of the paint adhesion though the corrosion resistance is 
improved. In order to obtain a lithium silicate film having a thickness 
within this range, it is preferred that the concentration of an aqueous 
solution of lithium silicate be 0.1 to 500 g/l, especially 5 to 200 g/l, 
as calculated as SiO.sub.2. From the viewpoint of the adaptability to the 
coating operation, it is preferred that the temperature of the lithium 
silicate solution be 0.degree. to 70.degree. C., especially 20.degree. to 
50.degree. C. If the solution temperature is lower than 0.degree. C., the 
solution is frozen and solidified, and if the solution temperature is 
higher than 70.degree. C., the tendency of solidification is enhanced and 
the solution becomes very unstable. 
Coating of lithium silicate can be accomplished by customary coating 
methods such as dip coating, spray coating, shower coating and roll 
coating. Drying of the coating is advantageously accomplished by hot air 
drying, and baking at a high temperature (100.degree. to 200.degree. C.) 
is not especially necessary. When the solution temperature is relatively 
high, the coating can sufficiently be dried by natural drying. 
Water washing is carried out for removing the alkaline component left on 
the surface of the lithium silicate film. The intended effect can 
sufficiently be attained by using water having a pH value of 6 to 8 which 
is customarily used for water washing. In order to remove the alkaline 
component completely, pickling may be performed. Water washing or pickling 
may be carried out not only at normal temperatures but also at lower or 
higher temperatures. A higher washing effect can be obtained at a higher 
temperature and the drying time can be shortened. Accordingly, a higher 
temperature is prefered from the viewpoint of the operation efficiency. 
If the above-mentioned lithium silicate film alone is formed, the corrosion 
resistance is insufficient in either the uncoated state or the coated 
state, and furthermore, the paint adhesion is extremely poor and no 
satisfactory surface-treated steel plate can be obtained. However, if this 
lithium silicate film is combined with an organic composite silicate film 
according to the present invention, an excellent surface-treated steel 
plate which is satisfactory in both the corrosion resistance and the paint 
adhesion can be obtained. 
The organic composite silicate film as the second layer will now be 
described in detail. 
The intended effect can be attained if the amount of the organic composite 
silicate film deposited on one surface is 0.1 to 4.0 g/m.sup.2, and it is 
preferred that this amount be 0.5 to 3.0 g/m.sup.2. If this amount is 
smaller than 0.1 g/m.sup.2, no substantial effect can be attained. If this 
amount is larger than 4 g/m.sup.2, the quality is improved to some extent 
but no prominent improvement can be attained, and therefore, the 
production becomes economically disadvantageous and continuous multiple 
spot welding is difficult, with the result that the practical utility of 
the surface-treated steel plate is drastically reduced. 
The sysnthesis of the organic composite silicate that is used in the 
present invention is performed according to the method disclosed in 
Japanese Patent Publication No. 34406/79. More specifically, the organic 
composite silicate can be obtained by mixing colloidal silica, a 
water-soluble or water-dispersible organic resin and a trialkoxysilane 
compound and reacting this three-component mixture at a temperature higher 
than 10.degree. C. but lower than the boiling point of the mixture. 
Colloidal silica is water-dispersible silica called "silica sol", and 
commercially available products supplied by Nissan Kagaku K.K., Du Pont 
Co., USA, and other companies may be directly used. An acidic or basic 
product is appropriately selected and used according to the stable pH 
range of the organic resin used. 
Any of organic resins capable of being stably mixed with colloidal silica 
can be used for formation of the organic composite silicate. For example, 
there can be used resins containing hydrophilic groups such as hydroxyl, 
carboxyl and amino groups, such as an acrylic copolymer, an alkyd resin, 
an epoxy resin, a fatty acid- or polybasic acid-modified polybutadiene 
resin, a polyamine resin and a polycarboxylic acid resin, and mixtures and 
addition condensates of two or more of them, so far as they are 
water-soluble or water-dispersible. 
A so-called silane coupling agent commercially available can be used as the 
trialkoxysilane compound as the third component of the organic composite 
silicate. For example, there can be mentioned vinyltriethoxysilane, 
vinyl-tris(.beta.-methoxyethoxy)silane, 
.gamma.-glycidoxypropyltrimethoxysilane, 
.gamma.-methacryloxypropyltrimethoxysilane, 
N-.beta.-(minoethyl)-.gamma.-aminopropyltrimethoxysilane and 
.gamma.-aminopropyltriethoxysilane. 
In the organic composite silicate that is used in the present invention, 
the colloidal silica/organic resin mixing weight ratio as solids is in the 
range of from 5/95 to 95/5, preferably from 20/80 to 50/50. It is 
preferred that the amount used of the silane compound as the third 
component be 0.5 to 15% by weight based on the total amount of the 
colloidal silica and organic resin as solids. 
In order to further improve the quality and capacity of the surface-treated 
steel plate, an alkoxide compound, an oxyacid of vanadium and a salt 
thereof may be added to a solution for the organic composite silicate 
treatment according to need. More specifically, if at least one member 
selected from these additives is added in an amount of up to 14% by 
weight, preferably 0.2 to 8% by weight, based on the total solids, the 
corrosion resistance of the coating can further be improved. 
Alkoxide compounds of titanium and zirconium are preferred as the alkoxide 
compound. The alkoxide compounds of titanium and zirconium are 
co-ordination compounds having a functionality of at least 2 (preferably 2 
or 3), which are formed by linking an alkoxide compound represented by the 
general formula R.sup.1.sub.2 M(R.sup.2).sub.2, R.sup.1 M(R.sup.2).sub.3 
or M(R.sup.2).sub.4 in which M stands for titanium or zirconium, R.sup.1 
stands for a substituent such as an ethyl, amyl, phenyl, vinyl, 
p-(3,4-epoxycyclohexyl), .gamma.-mercaptopropyl or aminoalkyl group and 
R.sup.2 stands for an alkoxy group having ordinarily 1 to 8 carbon atoms, 
such as a methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, 
sec-butoxy, tert-butoxy, n-pentoxy, isopentoxy, n-hexethoxy, n-heptoxy or 
n-octoxy group, with a ligand selected from a dicarboxylic acid such as 
maleic acid, a hydroxycarboxylic acid such as lactic acid or tartaric 
acid, ethylene glycol, a diketone such as diacetone alcohol or acetyl 
acetone, an ester such as ethyl acetoacetate or ethyl malonate, a ketone 
ester, salicylic acid, catechol, pyrogallol or an alkanol amine such as 
triethanol amine, diethanol amine or dimethylaminoethanol. 
The oxyacid of vanadium and its salt includes vanadium trioxide (V.sub.2 
O.sub.3), vanadium pentoxide (V.sub.2 O.sub.5), lithium orthovanadate 
(Li.sub.3 VO.sub.4), sodium orthovanadate (Na.sub.3 VO.sub.4), lithium 
metavanadate (LiVO.sub.3.2H.sub.2 O), potassium metavanadate (KVO.sub.3), 
sodium metavanadate (NaVO.sub.3.4H.sub.2 O), ammonium metavanadate 
(NH.sub.4 VO.sub.3) and sodium pyrovanadate (Na.sub.4 V.sub.2 O.sub.7). 
The additive mentioned above is added in the above-described preferred 
amount. If the additive is added in an excessive amount, the effect of the 
organic composite silicate film is reduced and the properties of the 
surface-treated steel plate are degraded. Furthermore, the crosslinking 
reaction is promptly advanced and the viscosity of the treating solution 
is increased, and no good results can be obtained. 
It is believed that the above-mentioned additive acts as a crosslinking 
agent and reduces the amount of hydrophilic groups left in the organic 
composite silicate film to increase the crosslinking density of the film, 
with the result that the corrosion resistance of the coating is improved. 
The organic composite silicate may be coated, as in case of lithium 
silicate, by customary coating methods such as dip coating, spray coating, 
shower coating and roll coating. 
The zinc or zinc alloy plating layer to be formed on the starting steel 
plate in the present invention will now be described. 
Deposition of zinc or a zinc alloy may be accomplished according to a 
customary electroplating method or hot dipping method. At least one 
element selected from Fe, Ni, Al, Co, Cr, Mo, W, Pb and Sn is added to the 
zinc or zinc alloy plating solution.

The present invention will now be described in detail with reference to the 
following Example that by no means limits the scope of the invention. 
EXAMPLE 
Acrylic composite silicate and epoxy composite silicate were first 
synthesized according to the following procedures. 
[A] Synthesis of Acrylic Composite Silicate 
A four-neck flask having a capacity of 1 liter, which was provided with a 
thermometer, a stirrer, a cooler and a dropping funnel, was charged with 
180 parts of isopropyl alcohol, and the inside atmosphere was replaced by 
nitrogen and the inner temperature of the flask was adjusted to about 
85.degree. C. Then, a monomer mixture comprising 140 parts of ethyl 
acrylate, 68 parts of methyl methacrylate, 15 parts of styrene, 15 parts 
of N-n-butoxymethyl acrylamide, 38 parts of 2-hydroxyethyl acrylate and 24 
parts of acrylic acid, together with a catalyst consisting of 6 parts of 
2,2'-azobis(2,4-dimethylvaleronitrile), was added dropwise to the charge 
of the flask over a period of about 2 hours. After completion of the 
dropwise addition, reaction was conducted for 5 hours at the same 
temperature to obtain a colorless transparent resin solution having a 
solid content of 63% and an acid value of 67. Then, 45 parts of 38% 
aqueous ammonia was incorporated into 500 parts of the so-obtained 
acrylic copolymer resin solution, and water was added to the mixture and 
the mixture was sufficiently stirred to obtain an aqueous dispersion of an 
acrylic copolymer having a solid content of 20% and a pH value of 9.5. A 
flask was charged with 300 parts of this aqueous dispersion, and a 
predetermined amount of colloidal silica (supplied under the tradename of 
"Snowtex N" by Nissan Kagaku Kogyo K.K.) was added at room temperature 
with sufficient stirring. Then, 1 part of 
.gamma.-methacryloxypropyltrimethoxysilane (supplied under the tradename 
of "KBM 503" by Shinetsu Kagaku Kogyo K.K.) was dropped to the charge of 
the flask with stirring, and the mixture was heated at 85.degree. C. and 
maintained at this temperature for 2 hours to effect reaction, whereby a 
milky white, water-dispersible acrylic composite silicate having a solid 
content of 20% and a silicate content of 40% as solids was obtained. 
[B] Synthesis of Epoxy Composite Silicate 
A flask was charged with 62 parts of a bisphenol A type epoxy resin having 
an epoxy equivalent of 950 (supplied under the tradename of "Epikote 1004" 
by Shell Chemical Co.), 19 parts of linseed oil, 19 parts of tung oil and 3 
parts of xylene, and the mixture was gradually heated to 240.degree. C. 
under circulation of nitrogen and was fluxed for 2 hours at this 
temperature. Then, the reaction mixture was cooled, and when the 
temperature was lowered to 70.degree. C., 40 parts of ethylene glycol 
monoethyl ether was added to the mixture to obtain a fatty acid-modified 
epoxy resin solution having a solid content of about 70%, an acid value of 
about 54 and a hydroxyl group equivalent of about 520. According to the 
same method as described above with respect to the acrylic composite 
silicate [A], an epoxy composite silicate was obtained by using the 
so-prepared epoxy resin. 
An electrically zinc-plated steel plate (the amount deposited on one 
surface was 20 g/m.sup.2) and a zinc alloy-dip-plated steel plate (the 
amount deposited on one surface was 60 g/m.sup.2) were treated by using 
the organic composite silicate treating solutions prepared in [A] and [B] 
above according to the following treating process to obtain sample plates 
shown in Tables 1 and 2. Treated steel plates outside the scope of the 
present invention and phosphate-treated and chromate-treated steel plates 
were used as comparative plates. 
______________________________________ 
[Treating Process] 
______________________________________ 
Electrically zinc-plated steel plate or zinc alloy-dip-plated 
steel plate 
.dwnarw. 
Surface cleaning (alkali degreasing) 
.dwnarw. 
Coating of lithium silicate (concentration of 40 g/l, room 
temperature, roll coating) 
.dwnarw. 
Hot air drying 
.dwnarw. 
Hot water washing (60.degree. C.) 
.dwnarw. 
Coating of organic composite silicate (concentration of 
200 g/l, room temperature, roll coating) 
.dwnarw. 
Hot air drying 
______________________________________ 
The sample plates prepared according to the above-mentioned treating 
process and the comparative plates are shown in Tables 1 and 2, and the 
results of the tests made on these plates are shown in Tables 3 and 4. 
From the test results shown in Tables 3 and 4, it will readily be 
understood that the surface-treated steel plate of the present invention 
is excellent over the conventional phosphate-treated or chromate-treated 
steel plate and is well-balanced in properties and capacities. 
TABLE 1 
______________________________________ 
Plates of the present invention prepared from 
electrically zinc-plated steel plate (deposited 
amount of 20 g/m.sup.2 on each surface) and comparative 
plates (underline indicates feature outside scope 
of the present invention) 
Organic composite 
Lithium .multidot. Silicate Film 
silicate Film 
Amount Amount 
deposited deposited 
No Kind (g/m.sup.2) 
Kind (g/m.sup.2) 
______________________________________ 
Plates of the invention 
1 Li.sub.2 O.7.5SiO.sub.2 
0.005 .sup. A + B.sup.1 
2.0 
2 " 0.05 " " 
3 " 0.2 " " 
4 " " " 0.5 
5 Li.sub.2 O.3.5SiO.sub.2 
" " 2.0 
6 Li.sub.2 O.4.5SiO.sub.2 
" " " 
7 Li.sub.2 O.10.0SiO.sub.2 
" " " 
8 " " A.sup.2 " 
Comparative plates 
9 Li.sub.2 O.7.5SiO.sub.2 
0.0005 A + B " 
10 " 2.0 " " 
11 " 0.2 " 0.05 
12 " " " 5.0 
13 Li.sub.2 O.7.5SiO.sub.2 
0.2 -- -- 
14 -- -- A + B 2.0 
15 Li.sub.2 O. --1.0SiO.sub.2 
0.2 " " 
16 Colloidal silica 
" " " 
17 Phosphate-treated (with chromium sealing) 
Conven- 
tional 
18 Chromate-treated products 
______________________________________ 
NOTE: 
A + B: Treating solution comprising 60 parts (as solids) of the acrylic 
composite silicate and 40 parts (as solids) of the epoxy composite 
silicate 
A: Treating solution comprising 100 parts (as solids) of the acrylic 
composite silicate 
TABLE 2 
______________________________________ 
Plates of the present invention prepared from 
zinc-dip-plated steel plate (deposited amount 
of 60 g/m.sup.2 on each surface) and comparative plates 
(underline indicates feature outside scope of the 
present invention) 
Organic Composite 
Lithium .multidot. Silicate Film 
silicate Film 
Amount Amount 
deposited deposited 
No Kind (g/m.sup.2) 
Kind (g/m.sup.2) 
______________________________________ 
Plates of the invention 
1' Li.sub.2 O.7.5SiO.sub.2 
0.005 A + B.sup.1 
2.0 
2' " " " " 
3' " 0.2 " " 
4' " " " 0.5 
5' Li.sub.2 O.3.5SiO.sub.2 
" " 2.0 
6' Li.sub.2 O.4.5SiO.sub.2 
" " " 
7' Li.sub.2 O.10.0SiO.sub.2 
" " " 
8' " " A.sup.2 " 
Comparative plates 
9' Li.sub.2 O.7.5SiO.sub.2 
0.0005 A + B " 
10' " 2.0 " " 
11' " 0.2 " 0.05 
12' " " " 5.0 
13' Li.sub.2 O.7.5SiO.sub.2 
0.2 -- -- 
14' -- -- A + B 2.0 
15' Li.sub.2 O. --1.0SiO.sub.2 
0.2 " " 
16' Colloidal silica 
" " " 
17' Phosphate-treated (with chromium sealing) 
Conven- 
tional 
Chromate-treated products 
______________________________________ 
NOTE: 
A + B: Treating solution comprising 60 parts (as solids) of the acrylic 
composite silicate and 40 parts (as solids) of the epoxy composite 
silicate 
A: Treating solution comprising 100 parts (as solids) of the acrylic 
composite silicate 
TABLE 3 
__________________________________________________________________________ 
Test results of plates prepared from electrically zinc-plated steel 
plate 
and comparative plates 
Primary corrosion 
Primary corrosion 
Secondary corrosion 
resistance.sup.3 
Boiling water 
resistance.sup.1 
resistance.sup.2 
Lattice 
Lattice cut 
resistance.sup.4 
No 48 h 240 h 
(SST 240 h) 
cut test 
Erichsen test 
30 min 
180 min 
Remarks 
__________________________________________________________________________ 
Plates of the 
1 .circle. 
x .DELTA.-.circle. 
.circleincircle. 
.circle. 
.circleincircle. 
.circleincircle. 
invention 
2 .circle. 
.DELTA. 
.DELTA.-.circle. 
.circleincircle. 
.circle. 
.circleincircle. 
.circleincircle. 
3 .circle.-.circleincircle. 
.DELTA. 
.circle. .circleincircle. 
.circle. 
.circleincircle. 
.circleincircle. 
4 .circle. 
x-.DELTA. 
.circle. .circleincircle. 
.circle. 
.circleincircle. 
.circle. 
5 .circle.-.circleincircle. 
.DELTA. 
.DELTA.-.circle. 
.circleincircle. 
.circle. 
.circleincircle. 
.DELTA.-.circle. 
6 .circle.-.circleincircle. 
.DELTA. 
.circle. .circleincircle. 
.circle. 
.circleincircle. 
.circle. 
7 .circle. 
x .circle. .circleincircle. 
.circle. 
.circleincircle. 
.circleincircle. 
8 .circle. 
x .circle. .circle.-.circleincircle. 
.circle. 
.circleincircle. 
.circleincircle. 
Comparative 
9 .DELTA. 
x x x .circleincircle. 
.circle. 
.circleincircle. 
.circleincircle. 
plates 10 .circle.-.circleincircle. 
.DELTA. 
.DELTA. .DELTA. 
x .circle. 
.DELTA. 
11 .DELTA. 
x x .DELTA. .circleincircle. 
.circle. 
.circle. 
.DELTA. 
12 .circle.-.circleincircle. 
.DELTA.-.circle. 
.circle. .circleincircle. 
.circle. 
.circleincircle. 
.circleincircle. 
(A) 
13 x x x x x .circle. 
x x x x x x 
14 .DELTA. 
x x x .circleincircle. 
.circle. 
.circleincircle. 
.circleincircle. 
15 .DELTA. 
x x .DELTA. 
x .DELTA. 
x x 
16 .DELTA. 
x x x-.DELTA. .circleincircle. 
.circle. 
.circleincircle. 
.circleincircle. 
17 .circle. 
x x .DELTA.-.circle. 
.circleincircle. 
.circle. 
.circleincircle. 
.circle. 
(B) 
18 .circle. 
x x .DELTA. .circleincircle. 
.DELTA. 
.circle. 
.DELTA. 
__________________________________________________________________________ 
NOTE: 
(A): Spot welding impossible, 
(B): Conventional product 
TABLE 4 
__________________________________________________________________________ 
Tests results of the present invention prepared from zinc-dip-plated 
steel plate 
and comparative plates 
Primary corrosion 
Primary corrosion 
Secondary corrosion 
resistance.sup.3 
Boiling water 
resistance.sup.1 
resistance.sup.2 
Lattice 
Lattice cut 
resistance.sup.4 
No 48 h 240 h 
(SST 240 h) 
cut test 
Erichsen test 
30 min 
180 min 
Remarks 
__________________________________________________________________________ 
Plates of the 
1' 
.circle. 
x-.DELTA. 
.circle. .circleincircle. 
.circle. 
.circleincircle. 
.circleincircle. 
invention 
2' 
.circle.-.circleincircle. 
.DELTA. 
.circle.-.circleincircle. 
.circleincircle. 
.circle. 
.circleincircle. 
.circleincircle. 
3' 
.circle.-.circleincircle. 
.DELTA. 
.circleincircle. 
.circleincircle. 
.circle. 
.circleincircle. 
.circleincircle. 
4' 
.circle.-.circleincircle. 
.DELTA. 
.circle.-.circleincircle. 
.circleincircle. 
.circle. 
.circleincircle. 
.circleincircle. 
5' 
.circle.-.circleincircle. 
.DELTA. 
.circle. .circleincircle. 
.circle. 
.circleincircle. 
.DELTA.-.circle. 
6' 
.circle.-.circleincircle. 
.DELTA. 
.circleincircle. 
.circleincircle. 
.circle. 
.circleincircle. 
.circleincircle. 
7' 
.circle. 
.DELTA. 
.circleincircle. 
.circleincircle. 
.circle. 
.circleincircle. 
.circleincircle. 
8' 
.circle. 
.DELTA. 
.circleincircle. 
.circleincircle. 
.circle. 
.circleincircle. 
.circleincircle. 
Comparative 
9' 
.DELTA. 
x .DELTA. .circleincircle. 
.circle. 
.circleincircle. 
.circleincircle. 
plates 10' 
.circle.-.circleincircle. 
.DELTA.-.circle. 
.DELTA. .DELTA. 
.DELTA. 
.circle. 
.DELTA. 
11' 
.DELTA. 
x .DELTA. .circleincircle. 
.circle. 
.circleincircle. 
.DELTA. 
12' 
.circle.-.circleincircle. 
.circle. 
.circleincircle. 
.circleincircle. 
.circle. 
.circleincircle. 
.circleincircle. 
(A) 
13' 
.DELTA. 
x x .circle. 
x x x x x 
14' 
.DELTA. 
x .DELTA. .circleincircle. 
.circle. 
.circleincircle. 
.circleincircle. 
15' 
.DELTA. 
x .DELTA. .DELTA. 
x .DELTA. 
x x 
16' 
.DELTA. 
x .DELTA. .circleincircle. 
.circle. 
.circleincircle. 
.circleincircle. 
17' 
.circle. 
x .circle. .circleincircle. 
.circle. 
.circle. 
.DELTA. 
(B) 
__________________________________________________________________________ 
NOTE: 
(A): Spot welding impossible, 
(B): Conventional product 
Note 
(1) Primary Corrosion Resistance 
The uncoated surface-treated steel plate was subjected to the salt spray 
test for 24 hours and 240 hours according to the method of JIS Z-2371, and 
the white rust-appearing area was measured and the primary corrosion 
resistance was evaluated according to the following scale: 
______________________________________ 
Evaluation White Rust-Appearing Area 
______________________________________ 
.circleincircle. 
no 
.circle. 1-10% 
.DELTA. 11-25% 
x 26-50% 
xx more than 50% or red rust 
______________________________________ 
(2) Secondary Corrosion Resistance (Corrosion Resistance of Coating) 
A melamine-alkyd resin type paint (baked at at 140.degree. C. for 20 
minutes, film thickness of 30.mu., pencil hardness of H to 2 H) was 
coated, and cross cuts were formed on the coating and the salt spray test 
was carried out for 240 hours according to the method of JIS Z-2371. The 
sample was then allowed to stand in a room for about 12 hours and an 
adhesive cellophane tape was applied to the cross-cut coating. The tape 
was instantaneously peeled and the average peel width (mm) on one side was 
calculated according to the following formula: 
##EQU1## 
______________________________________ 
Evaluation of Average Peel 
Width on One Side Average Peel Width 
______________________________________ 
.circleincircle. 0-0.5 mm 
.circle. 0.6-1.0 mm 
.DELTA. 1.1-2.0 mm 
x 2.1-3.0 mm 
xx 3.1 mm or more 
______________________________________ 
(3) Primary Adhesion (Paint Adhesion) 
The above-mentioned paint was coated and, the square cut adhesion test and 
square cut Erichsen test were carried out and the damages on the coated 
surface were examined. 
Square Cut Adhesion Test 
Eleven cut lines were formed at intervals of 1 mm in either the 
longitudinal direction or the lateral direction to form 100 square cuts, 
and an adhesive cellpophane tape was applied to the cut coated surface and 
was instantaneously peeled. 
Cut Erchsen Test 
Square cuts were formed in the above-mentioned manner, and the sample was 
extruded by an Erichsen extruder and an adhesive cellophane tape was 
applied and instantaneously peeled. 
The results of the square cut test and square cut Erichsen test were 
evaluated according to the following scale: 
______________________________________ 
Evaluation Damages on Surface of Coating 
______________________________________ 
.circleincircle. 
no change 
.circle. slight peeling of coating 
.DELTA. some peeling of coating 
x considerable peeling of coating 
xx peeling of major portion of coating 
______________________________________ 
(4) Boiling Water Resistance 
The above-mentioned paint was coated and the coated plate was dipped in 
boiling water for a predetermined time (30 minutes or 180 minutes), and 
formation of blisters was checked. 
______________________________________ 
Evaluation 
Formation of Blister on Surface of Coating 
______________________________________ 
.circleincircle. 
no blister 
.circle. a few (several) blisters 
.DELTA. some blisters 
x considerable blisters 
xx large blisters on entire coating surface 
______________________________________