CA2168437A1 - Surface coating method - Google Patents

Surface coating method

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Publication number
CA2168437A1
CA2168437A1 CA 2168437 CA2168437A CA2168437A1 CA 2168437 A1 CA2168437 A1 CA 2168437A1 CA 2168437 CA2168437 CA 2168437 CA 2168437 A CA2168437 A CA 2168437A CA 2168437 A1 CA2168437 A1 CA 2168437A1
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Prior art keywords
coating method
surface coating
weight
composition
coating
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CA 2168437
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French (fr)
Inventor
Michiaki Nakazato
Kazuaki Sugano
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Nippon Dacro Shamrock Co Ltd
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Individual
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    • CCHEMISTRY; METALLURGY
    • C07ORGANIC CHEMISTRY
    • C07KPEPTIDES
    • C07K14/00Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof
    • C07K14/81Protease inhibitors
    • C07K14/815Protease inhibitors from leeches, e.g. hirudin, eglin
    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09DCOATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D5/00Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
    • C09D5/08Anti-corrosive paints
    • C09D5/10Anti-corrosive paints containing metal dust
    • C09D5/106Anti-corrosive paints containing metal dust containing Zn
    • CCHEMISTRY; METALLURGY
    • C23COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23CCOATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C22/00Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C22/73Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals characterised by the process
    • C23C22/74Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals characterised by the process for obtaining burned-in conversion coatings

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Health & Medical Sciences (AREA)
  • Materials Engineering (AREA)
  • Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Biophysics (AREA)
  • Gastroenterology & Hepatology (AREA)
  • Genetics & Genomics (AREA)
  • Medicinal Chemistry (AREA)
  • Molecular Biology (AREA)
  • Proteomics, Peptides & Aminoacids (AREA)
  • Biochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Health & Medical Sciences (AREA)
  • Tropical Medicine & Parasitology (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Wood Science & Technology (AREA)
  • Chemical Treatment Of Metals (AREA)
  • Application Of Or Painting With Fluid Materials (AREA)
  • Paints Or Removers (AREA)
  • Other Surface Treatments For Metallic Materials (AREA)
  • Laminated Bodies (AREA)

Abstract

A surface coating method is provided which can make an anticorrosive coating film having a high corrosive resistance with reduced man-hour and low costs. The method comprises coating a metal substrate with a bake-type metal anticorrosive composition containing a water-soluble chromate compound and zinc powder, baking the coated metal substrate, immediately followed by dipping the baked metal substrate into a liquid composition either or both or a chromate compound and a resin monomer.

Description

-l- 2168~37 ~ SURFACE COATIN~ METHOD
BACKGROUND OF THE INVENTION
Field of the Invention The present invention relates to a surface coating method, more particularly to a method of forming a coating film having a high corrosion resistance on a metal surface.

Description of ~elated Art Various coating compositions for use in preventing corro-sion of a me~al such as steel are well-known. For example, a metal anticorrosive composition containing cllromic anhydride and a powder of a metal such as zinc and aluminum is disclosed by JP 60-50228(B) as a coating composition exhibiting superior properties. As such a coating composition, Dacrodip (trade-mar~ is commercially available.
This Dacrodip normally supplied to users comprises a com-bination of a first component mainly comprised of chromic an-hydride and water with a second component comprised of a metal powder and a low-molecular-weight oxohydroxyether such as propylene glycol, and in addition a thickener. Wllen Dacrodip is used, users mix the first component, the second component and a thickener and apply a predetermined amount of tlle mix-ture on~o a metal substrate which is to be provided with a coating film. l~he applied amount may be normally one which is required to provide a thickness of several micrometers. Then, ~he applied metal substr~te may be heated to abou~ 300C for a predetermined period of time to form a coating film on the metal substrate.
This coating film exhibits an excellent resistance to corrosion by brines, but recently higher resistance has been in demand. In order to meet this demand, the coating treat-ment as mentioned above, which is hereinafter referred to as - "the first coating step~, has often been followed by an addi-tional chromating step or coating step, which is referred to as ~the second coating step". The second coating step follow-ing the first step makes it possible to meet the demanded an-ticorrosion, but increases the number of steps to include nearly two-fold steps, because the first coating step includes coating, baking and coolinq and the second coating step also ~Nr~

wo ~ 2 1 6 8 q 3 7 ~/.~/0~29 includes coating, baking and cooling. There is such a problem that the treating time and costs are greatly increased.

SUMMA~Y OF THE INVENTION
The object of the present invention is to solve the above-mentioned problem and to proYide a method of forming an anticorrosive coating film on a metal surface with a reduced number of steps and lower costs.
The first aspect of the present invention is a method of surface coating a metal substrate with a ba~e-type metal anti-corrosive composition comprising a water-soluble chromate com-pound and zinc powder and baking the coated metal substrate, immediately followed by dipping the baked metal substrate into a liquid cu~osition cont~in;ng a chromate compound and/or a resin.
The second aspect of the present invention is the method of surface coating according to the first aspect, wherein the baked metal substrate is ~ipp~ into the above-mentioned liq-uid composition, while the substrate is being maintained at a temperature of 50C or higher.
The third aspect of the present invention is the method of surface coating according to the first or second aspect, wherein the dipping is carried out for a period of 30 minutes or less.

DETATT-~n DESCRIPTION OF ~K~:~KED EMBODIMENTS OF THE lNv~.LlON
The bake-type metal anticorrosive composition used in the present invention should contain a water-soluble chromate com-pound and zinc powder.
The water-soluble chromate compounds used herein are not specified but all known, for example, they may be chromic acid, a water-soluble metal salt of chromic acid such as cal-cium chromate and magnesium chromate and a dichromate such as zinc dichromate, potassium dichromate, sodium dichromate, mag-nesium dichromate and calcium dichromate.
The zinc powders used herein may be in any shape. Of these powders, zinc flakes are preferred, particularly prefer-ably the flakes have a thickness of 0.1-0.5 ym and a length of W095/~3 3 2 1 6 8 4 3 7 PCT/~ 4/01291 up to 15 ~m. The zinc powder may be used together with an aluminum powder.
The content of the water-soluble chromate compound is in the range of 1-12% by weight, preferably 2-8~ by weight, based on the weight of the final composition. The content of the zinc powder is in the range of 10-40% by weight, preferably 15-30% by weight, based on the weight of the final composi-tion.
The bake-type metal anticorrosive composition contains not only the water-soluble chromate compound and the zinc pow-der but also may contain a boric acid or boron oxide, a low-molecular-weight oxohydlo~ye her and a pH adjuster, a wetting agent, and water and/or an organic solvent, as desired.
As the boric acid is preferred commercially available or-thoboric acid. If necessary, metaboric acid or tetraboric acid may be used in place of or in combination with the ortho-boric acid. In the case where boric acid and/or boric oxide is used, the content thereof in the bake-type metal anticorro-sive c~ sition is nQrr~lly in the range of 1~-75% by weight, preferably 15-50% by weight, basëd on the total weight of the boric acid and/or boric oxide and the water-soluble chromate compound. The content of boric acid and~or boric oxide within this range provides the composition with a good anticorrosion in both environments of brine and plain water.
The low-molecular-weight oxohydLo~yeLher may be glycol or a low-molecular-weight ether-type polymer thereof. For exam-ple, it may be ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tri~lopylene glycol, diacetone alcohol or members of similar groups, or mixtures thereof. These ethers can act as a reducing agent for the water-soluble chromate c~lu~ound to change in the chro-mate compound, and make it easy to form a uniform anticorro-sive coating film, because the ethers can gr~ y wor~ while the coating film is being formed by applying and baking the bake-type metal anticorrosive composition, to thereby prevent the boiling of the solvent, etc.
The pH adjuster is effectively used when the water-solu-ble chromate compound is strongly acidic, and it is used for adjusting the pH of the mixed solution within the range of wo gsl~ 4 2 i 6 8 4 3 7 ~1~4/0l29l :
-3.0-6.0 and normally selected from an oxide and hydroxide of a metal such as lithium or an element of Group IIA and Groups of higher numbers than IIA, such as strontium, calcium, barium, magnesium, zinc, cadmium and etc. The pH adjuster can keep the storage stability of the bake-type metal anticorrosive composition in an optimum state to prevent rapid reaction of the zinc powder and the acids in the liquid, which reaction causes degradation of the adhesion of the coating film and darkening of the appearance of the coating film.
A wetting agent may be used for assisting the suspension and dispersion of the zinc powder, and it may be a nonionic surface active agent, particularly an alkylphenol polyethoxy adduct, for example, ~Nopco 1592~ (tr~^~ r~) made by ~iamond Shamrock C~ c~l Co.
The bake-type metal anticorrosive composition used in the present invention may be prepared by mixing the above-men-tioned components by a known process, for example, using a high-speed mixer.
As the bake-type metal anticoLLosive co~.~osition is pre-ferred a composition (commercially available under tradename of ~Dacrodipn) which contains chromic anhydride, a metal such as zinc or aluminum, a pH adjuster of an oxide or hydroxide of a metal, a low-molec~ r-weight oxohydroxyether such as a polyglycol and a solvent, which is disclosed by JP 60-50228(B).
Normally, this bake-type metal anticorrosive composition is supplied to users in a combined form of a first component mainly comprised of chromic anhydride and water, with a second component comprised of the metal powder and the low-molecular-weight oxohydroxyether and the thickener.
Users mix the first component, the second component and the thickener i~me~i~tely before use, and then apply a prede-termined quantity of the mixture onto a metal substrate to be coated with the coating film. The applied quantity is nor-mally one which is required to finally form the coating film of several micrometers or more. Subsequentiy, the coated metal substrate is heated to a temperature o~ about 300C for a predetermined period of time to thereby form the coa~ing film on the metal substrate.

wo gs/0~3 5 2 1 6 8 4 ~ 7 ~,~4,0l2gl The metal substrate is not limited in the size and shape thereof and already known. The method of the present inven-tion is particularly advantageous for pl~ven~ing the corrosion of steels and hence often used for steel substrates. This method is preferably carried out after dusts or fats are removed from the surfaces of the substrates by an Alk~l;
cleaner or a chlorinated solvent.
The method of coating the bake-type metal anticorrosive composition on the metal substrates comprises the composition-applying step and the hAk;ng step.
The applying step may be carried out by a known way, for example, brushing, rAt~;ng, &~ayingr hot sprayingt air spray-ing, electrostatic coating, roller coating, curtain f7OW coat-ing, dip coating, electro~positing, spatula coating, etc. In the case where the dip coating is carried out, an excess of the composition may be removed by centrifuge or vibration after the dipping.
The baking step is carried out by using a hot air circu-lation furnace (LPG-burning furnace or electric furnace), far infrared ray heating furnace, infrared ray heating furnace, radiofrequency induction furnace, etc. or combinations of these furnaces. The heat treatment is carried out at a tem-perature of 180C or higher for a period of at least 0.2 sec-ond, preferably at a temperature of 200C or higher for a period of at least o.S second, more preferably at a tempera-ture of 260C or higher for a period of at least 0.5 second.
The coating may be repeated, as desired.
The coating film made on the metal substrate is normally 1 ~m thick or more, more preferably 3 ~m thick or more. This thickness is required to exhibit more stably resistant to corrosion.
In the method of the present invention, the coated metal substrate is dipped into a liquid composition cont~;n;ng a chromate c~ound and/or a resin immediately after the baking step in the coating process.
The terms n~ipre~ immediately after the baking step~ or ~baking ..., immediately followed by dipping~ used herein means that the baked metal substrate is dipped while it does not completely cool. Thus, the dipping is carried out before wo~&~ 6 2168~37 PCTt~4/01291 -the substrate cools completely. The temperature of the sub-strate to be dipped may be 50C or higher, normally 50-350C, more preferably 100-300C. If this temperature is within the range of S0-350C, a beautiful coating film can particularly be formed.
The liquid c~osition cont~in;ng-a chromate compound and/or a resin monomer may be in general one capable of being applied and then dried to form the coating film.
The chromate compound cont~ine~ in the liquid composition may be the same as water-soluble chromate compound contained in the bake-type metal anticorrosive composition. The ~ind of the chromate compound used in the dipping may be identical with or different from the kind of the water-soluble chromate compound used in the bake-type metal anticol.osive composi-tion. The chromate compounds used in the dipping may be used singly or in combination.
As the resin may be made reference to a water-soluble resin, a resin in aqueous emulsion, or a resin in aqueous sus-pension. Examples of the resins are an acryl resin, polyester resin, polyethylene resin, polyvinyl resin, epoxy resin, buta-diene resin, melamine resin, alkyd resin, phenol resin, etc.
Of these resins is preferred the acryl resin.
The liquid composition may contain the chromate compound without cont~;ning the resin, contain the resin without con-t~in;ng the chromate compound, or contain both the chromate compound and the resin. In the present invention, the liquid composition cont~ining both chromate compound and resin is preferred. The liquid c~osition cont~ining both chromate compound and resin normally contains 0.1-50% by weight, preferably 0.5-30% by weight, of the chromate compound and normally 0.5-40% by weight, preferably 0.5-20% by weight, of the resin.
As the liquid composition may be preferably made refer-ence to a chromation liquid commercially available as Dacromet #100" made by Nippon Dacro Shamrock K.K. and a resin coating agent commercially available as ~Dacromet LTX" made by Nippon Dacro Sh~mrock K.K.
In the case where the liquid composition contains a solid content, the solid content thereof is preferably adjusted to w095/ou~3 2 1 6 8 4 3 ~ PCT/~410~91 0.5-90% by weight, more preferably to 1-50% by weight. If the solid content is in the range of 0.5-90% by weight, a coating film having a beautiful appearance and a proper thickness can be obtained.
In the surface treating method according to the present invention, the temperature of the l`iquid composition may be Lmportant. If the tempela~ure of the liquid composition is excessively low, the cooling effect is too high to properly form the coating film. If the temperature of the liquid com-position is excessively high, on the other hand, the liquid composition itself may be degraded. The temperature of the liquid co-~L~ition may vary depending upon the temperature of the metal substrate, normally preferred to be adjusted to the range of 5-95C.
The metal substrate baked in the coating step is dipped in the liquid composition preferably for 20 minutes or less, normally O.l second to 30 minutes, preferably 0.5 second to 5 minutes. If the dipping time is in the range of O.l second to 30 minutes, the coating film can fully be formed on the metal substrate and, furthermore, the temperature of the substrate is not excessively l~eLed and hence the drying effect by the baking of the coating step is not lost.
According to the present invention, no baking is normally needed after the dipping step. However, a simple drying may be carried out, as desired.
The ~;rr;ng step forms a coating film of nQr~lly O.l ym thick or more, preferably l ~m thick or more. The coating film of l ~m thick or more is preferred, since it makes it possible to afford a more stable corrosion resistance to the coating film made by the first coating step.

The present invention will be illustrated below with ref-erence to some examples, but it is not lLmited to these exam-ples.
Evaluation of the coating films fabricated in the exam-ples was made in the following manner:

w~ gslo4~ 2 1 6 8 ~ 3 ~ PCT1nn~10~91 1. Appearance Thinness and unevenness of the coating films were visu-ally observed. Evaluation is classified in three criteria:
v ~ Very good G ---------- Good P ........... Poor - -G-P Somewhat poor but no practical problem 2. Anticorrosion Performance After a composite cyclic corrosion test was conducted, occurrence of red rust was visually observed. Evaluation is classified in three criteria:
V -- Very good-G -- Good P ........... Poor G-P - Some~hat poor but no practical problems 3. Time Required for Working Time required for ~orking (man-hour) was evaluated rela-tively to Comparative Example l as a basis.

-, .
A bolt of M lO mild steel (entire length: about 47 mm;
weight: about 22 grams) which was washed with a solvent vapor and dry honed was used as a test substrate.

Example l In the coating step was used Dacrodip (trademark) as the bake-type metal antic~losive composition, which was made operable by mi~ing in accordance with the recipe. In the dip-ping step was used Dacromet #1008L (trademark; blac~ chromat-ing liquid) as the chromate compound-cont~ining liquid compo-sition, which was free of a resin. The composition of Dacromet is as follows:
Chromic acid about 4% by weight Zinc powder about 20% ~y weight The test substrate was dipped into Dacrodip, and an ex-cess of Dacrodip on the substrate was centrifugally removed.
In the baking stage, the test substrate was placed in an elec-trically-heated hot air circulation oven, heated until the test substrate reached 300C and maintained at the same tem-~o ~ u3 9 2 1 6 8 ~ ~ 7 PCTt~4/0~91 -perature for 5 minutes. When the test substrate removed from the oven cooled to 290C, it was dipped into Dacromet #lOOBL
regulated to 50C, pulled up in 1 second and dried.
The quantity of the coating film adhered to the test sub-strate in the coating step was 100 mg/dm2 and the quantity ad-hered in the dipping step was 50 mg/dm2 The dipping-finished test substrate was evaluated in the above-mentioned manner.
The results are shown in Table 1.

Example 2 The same ~loc~dures as in ~rle 1 were repeated, except the following:
As the liquid composition for dipping was used Dacromet LTX (trademark; clear) cont~;ning a resin but free of a chro-mate compound. After the hAking stage of the coating step, the test substrate was dipped into Dacromet L$X (trademark;
clear) when it cooled to 250C, and then rllle~ up in 2 sec-onds and dried.
The quantity of the coating film adhered to the test sub-strate by the coating step was 100 mg/dm2 and the quantity ad-hered in the dipping step was 80 mgJdm2. The dipping-finished test substrate was evaluated in the above-mentioned manner.
The results are shown in Table 1.

Example 3 The same ~ ch~l res as in Example 1 were repeated, except for the following:
The liquid composition used in the dipping step was Dacromet #lOO(trademark; a chromating liquid) cont~;n;ng a chromate compound and free of a resin. The dipping time was 5 seconds.
The quantity of the coating film adhered to the test sub-strate was 100 mg/dm2, and the quantity adhered in the dipping step was SO mg/dm2. The dipping-finished test substrate was evaluated in the above-mentioned m~nn~r, The results are shown in Table 1.

wo gS/~U~B 21 G 8 4 37 PCT/~/01291 Example 4 The same procedures as in Example 1 were repeated, except for the following:
Baking in the coating step was conducted by heating the test substrate to 350C in an electrically heated hot air cir-culation oven and the maint~;ning the substrate at the same temperature for 5 minutes. When the substrate removed from the oven cooled to 300C, it was dipped into the liquid compo-sition adjusted to 95C and pulled up in 5 seconds and dried.
The quantity of the coating film adhered to the test sub-strate was 100 mg/dm2, and the quantity adhered in the dipping step was 100 mg/dm2. The dipping-finished test substrate was evaluated in the above-mentioned manner. The results are shown in Table 1.

F~mrle 5 The same prore~l7res as in Example 1 were repeated, except for the following:
When a test substrate ~aked in the coating step and then r~m~ved from an electrically heated hot air circulation oven cooled to 270C, it was ~irr~ into the liquid composition ad-justed to 20C, and then pulled up in O.S seconds and dried.
The quantity of the coating film adhered to the test sub-strate in the coating step was 100 mg/dm2, and the quantity adhered in the dipping step was 30 mg/dm2. The dipping-fin-ished test substrate was evaluated in the above-mentioned man-ner. The results are shown in Table 1.

Example 6 The same procedures as in Example 1 were repeated, except for the coating step was twice repeated, followed by the dip-ping step.
The quantity of the coating film adhered-to the test sub-strate in the coating step was 200 mg/dm2, and the quantity adhered in the dipping step was 100 mg/dm2. The dipping-fin-ished test substrate was evaluated in the above-mentioned man-ner. The results are shown in Table 1.

wo gs/~ 1 1 2 1 6 8 4 3 7 ~r~4,0l29l Example 7 The same procedures as in Example 1 ~ere repeated, except for the following:
As the liquid composition in She dipping step was used Dacromet $100BL (trademark; chromating liquid) contA~;n;ng an aqueous 10% acrylic ester as resin-tmade by Showa Kobunshi K.~.~ added thereto.
The quantity of the coating film adhered to the test sub-strate in the coating step was 100 mg/dm2, and the quantity adhered in the dipping step was ~0 mg/dm2. The dipping-fin-ished test substrate was evaluated in the above-mentioned man-ner. The result are shown in Table 1.

Comparative Example 1 In the first coating step was used Dacrodip as the bake-type metal anti~-o osive composition, which was made operable by mixing in accordance with the recipe. In the second coat-ing step was used Dacromet #lOOBL (black chromation liquid) as the liquid cQ~rosition contA;ning a chromate compound and/or resin monomer.
A test substrate was dipped in the Dacrodip, and an ex-cess of the Dacrodip on the substrate was centrifugally re-moved. Then, the test substrate was baked by heating in an electrically heated hot air circulation oven to 300C and maintAining at the same temperature for 5 minutes. The test substrate removed from the oven was allowed to cool to room tem~ ure.
In the same manner as in the first coating step, the test substrate was dipped in Dacromet #lOOBL as the liquid COlll~OSi-tion, and an excess of the liquid composition on the substrate was centrifugally lel-oved. The test substrate was again baked by heating in the electrically heated hot air circulation oven to 250C and maint~;n;ng at the same temperat~re for 5 min-utes.
The quantity of the coating film adhered to the test sub-strate in the first coating step was 100 mg/dm2, and the quan-tity adhered in the second coating step was SO mg/dm2. The coating-finished test substrate was evaluated in the above-mentioned manner. The results are shown in Table 1.

wo gsl04~ 2 1 6 8 4 3 7 PCT/Ip~0~91 C~r~rative Example 2 The same procedures as in Comparative Example 1 were repeated, except for the following:
In the second coating step was used Dacromet LTX (clear), which is a resin coating agent. The baking in the second coating step was conducted by heating the test substrate to 100C and maint~ining it at the samë temperature for S minutes in the electrically heated hot air circulation oven. The test substrate removed from the oven was allowed to cool to room temperature.
In the first coating step, the quantity of the coating film adhered to the test substrate was 100 mg/dm2. The quan-tity adhered in the second coating step was 80 mg/dm2. The coating-finished test substrate was evaluated in the above-~entioned manner. The results are sh~wn in ~able 1.

Comparative Example 3 The same ~LG~I res as in Example 1 were repeated, ~e~
that the second coating step was not carried out.
The quantity of the coating film adhered to the test sub-strate was 100 mg/dm2. The coating-finished test substrate was evaluated in the above-mentioned manner. The results are show~ in Table 1.

Comparative ~F~le 4 The same coating step as in Example 6 was twice repeated, e~ce~ that the second step was not carried out.
The quantity of the coating film adhered to the test sub-strate was 200 mg/dm2. The coating-finished test substrate was evaluated in the above-mentioned ~nner. The results are shown in Table 1. ~-wo ~1~ 2 1 6 8 q 3 7 ~/~/0129 _ 13 Table 1 Appearance Anticorrosion TLme Required Performance For Workinq Example 1 v G 6 Example 2 V G-P 6 Example 3 V G 6 Example 4 V G 6 Example 5 V G 6 Example 6 V V 11 Example 7 v G 6 Comp. Exam. 1 P G-P 10 Comp. Exam. 2 P G-P g Comp. Exam. 3 P P S
Comp. Exam. 4 G G 10 Conventional surface coating methods require a drying apparatus in the ~i~p;ng step and thus require muçh ~an-hour and operating time. On the othe~ hand, the su~face çoating ~ethod of the pre$ent invention çan elL~inate the drying step in the coating step by utiliz;ng the high te~peratuxe of the me~al substrate in ~he h~;ng of the çoating step. T~erefore, the surface coating method of the present invention can sLm-plify the apparatuses and shorten the o~e4~ing time.
Therefore, the method of the present invention is not only effective in industries and con~ribute t~ saving of energies and environmental protection.

Claims (17)

WHAT IS CLAIMED IS:
1. A surface coating method which comprises coating a metal substrate on the surface thereof with a bake-type metal anti-corrosive composition containing a water-soluble chromate compound and a zinc powder, baking the coated metal substrate, and immediately dipping the baked metal substrate while having a temperature of 50°C or higher into a liquid composition containing either or both of a chromate compound and a resin and said method does not include a second baking step after said dipping step.
2. (deleted)
3. The surface coating method according to Claim 1, where-in the metal substrate is made of steel.
4. The surface coating method according to Claim 1, where-in the water-soluble chromate compound is chromic acid or a water-soluble metal salt of chromic acid such as calcium chromate, magnesium chromate, zinc dichromate, potassium dichromate, sodium dichromate, magnesium dichromate and calcium dichromate.
5. The surface coating method according to Claim 1, where-in the zinc powder is in a flake form.
6. The surface coating method according to Claim 5, where-in the flake form has a thickness of 0.1-0.5 µm and a length of up to 15 µm.
7. The surface coating method according to Claim 1, where-in the zinc powder is used together with an aluminum powder.
8. The surface coating method according to Claim 1, where-in the content of the water-soluble chromate is in the range of 1-12% by weight of the composition.
9. The surface coating method according to Claim 1, where-in the content of the water-soluble chromate is in the range of 1-8% by weight of the composition.
10. The surface coating method according to Claim 1, where-in the content of the zinc powder is in the range of 10-40%
by weight of the composition.
11. The surface coating method according to Claim 1, where-in the content of the zinc powder is in the range of 15-30%
by weight of the composition.
12. The surface coating method according to Claim 1, where-in the bake-type metal anticorrosive composition further contains a boric acid or boric oxide, a low-molecular-weight oxohydroxyether, a pH adjuster, a wetting agent, and/or an organic solvent.
13. The surface coating method according to Claim 12, wherein the boric acid is orthoboric acid, metaboric acid and/or tetraboric acid.
14. The surface coating method according to Claim 12, wherein the low-molecular-weight oxohydroxyether is a glycol or a low-molecular-weight ether-type polymer thereof.
15. The surface coating method according to Claim 14, wherein the low-molecular-weight oxohydroxyether is ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, diacetone alcohol or members of the similar groups, or mixtures there-of.
16. The surface coating method according to Claim 1, where-in the baked metal substrate is dipped in said liquid compo-sition for 30 minutes or less.
17. (deleted)
CA 2168437 1993-08-05 1994-08-04 Surface coating method Abandoned CA2168437A1 (en)

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JP19494093A JPH0748678A (en) 1993-08-05 1993-08-05 Surface coating method
JP5-194940 1993-08-05

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CA2168437A1 true CA2168437A1 (en) 1995-02-16

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CN (1) CN1128547A (en)
CA (1) CA2168437A1 (en)
HU (1) HUT74110A (en)
PL (1) PL312462A1 (en)
SI (1) SI9420039A (en)
SK (1) SK14796A3 (en)
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CN104004397B (en) * 2013-09-18 2017-01-25 中磁科技股份有限公司 Masking liquid used for surface protection of neodymium iron boron magnet, and preparation method thereof
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US2777785A (en) * 1953-07-30 1957-01-15 Heintz Mfg Co Composition for and method of treating metals as well as the treated product
US2846342A (en) * 1955-09-30 1958-08-05 Leo P Curtin Bonding coats for metal
GB1273413A (en) * 1968-05-17 1972-05-10 Diamond Shamrock Corp Improvements in or relating to coated metals
JPH0483889A (en) * 1990-07-27 1992-03-17 Nippon Dakuro Shamrock:Kk Corrosion-resistant coating composition

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WO1995004843A1 (en) 1995-02-16
EP0712448A1 (en) 1996-05-22
CN1128547A (en) 1996-08-07
JPH0748678A (en) 1995-02-21
SK14796A3 (en) 1997-01-08
PL312462A1 (en) 1996-04-29
SI9420039A (en) 1996-06-30
HUT74110A (en) 1996-11-28
HU9503769D0 (en) 1996-02-28

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