JP2012097329A - Finishing agent for chemical film containing no hexavalent chromium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem that all of the erosion-resistance, appearance, and a friction coefficient can not be satisfied although the surface nature is improved by processing by a finishing agent containing oxyacid ion of phosphorous and trivalent chrome in a conventional chemical film formed on the surface of metals such as bolts and nuts haing friction faces.SOLUTION: The finished film satisfying all of the excellent erosion resistance, friction property, and appearance is formed by bringing a base body having the chemical film into contact with the finishing agent aqueous solution containing one kind or more of ions selected from the trivalent chrome and aluminum, and one kind or more of ions selected from oxyacid ion of phosphorous, and further Mg, Ca, Sr, and Ba.

Description

  The present invention relates generally to a finish used after applying a chemical conversion coating on the surface of zinc, copper, nickel, silver, iron, cadmium, aluminum, magnesium, or alloys thereof. The present invention particularly relates to a finishing agent used after a chemical conversion coating is applied to the surface of an iron part subjected to zinc and zinc-based alloy plating.

  One method of surface treatment is chemical conversion film treatment. By forming a chemical conversion film on the surface of various metals or their alloys, various performances such as rust prevention and paint adhesion can be improved. This method is widely used. In addition, it is generally performed to obtain higher performance by using an overcoat technique for applying an inorganic film such as an organic film using various resins or a silicate on the chemical film.

  However, in general, the overcoat treatment is viscous to the coating agent used, and it is difficult to apply it uniformly or to dry it. In addition, when an overcoat is applied to fastening parts such as bolts, washers, and nuts with an organic coating agent, the coefficient of friction is greatly reduced due to the effect of the slip of the overcoat itself. Thus, in order to eliminate such drawbacks, development of finishing treatments and finishing agents as alternatives to overcoats has been underway.

  Japanese Patent Application Laid-Open No. 2005-320573 discloses an aqueous solution of a finishing agent containing phosphorus oxyacid ions and trivalent chromium. When a substrate having a trivalent chromium film is immersed in this aqueous solution, a finishing layer containing trivalent chromium and phosphorus is formed. As a result, the appearance and corrosion resistance can be improved, and the friction coefficient does not decrease so much.

  In recent years, chromium-free chemical coating treatment has been required as an environmental measure, and chromium-free finish treatment agents have been required for finishing treatment, but none have sufficient performance. This is the current situation.

JP-A-2005-320573

  The present invention provides a finishing agent and a finishing method that are all excellent in appearance, coefficient of friction and corrosion resistance by adding ions of a predetermined second group element to a finishing solution using existing trivalent chromium and phosphoric acid. provide. Furthermore, the use of a specific group 2 element ion makes it possible to form a finishing layer having sufficient performance even if trivalent chromium is partially substituted or completely changed to aluminum. A method is also provided.

  The present invention provides a substrate having a chemical conversion film on an aqueous finish solution containing one or more ions selected from trivalent chromium and aluminum, one or more ions selected from Mg, Ca, Sr and Ba together with phosphorus oxyacid ions To form a finish film containing trivalent chromium and / or aluminum, phosphorus, and Group 2 elements.

  By adding the above-mentioned Group 2 elements to the conventional finishing solution of phosphoric acid and trivalent chromium, the corrosion resistance of the conventional finishing treatment is greatly improved and the appearance improvement effect is maintained, and there is a problem of the coefficient of friction. As a result, a finishing process with no fastening problems was realized.

  As a result of adding the second group element, it can be confirmed that the water solubility of the finished film is lowered, and the corrosion resistance is thereby improved. The cause of the decrease in water solubility is unknown, but it can be presumed that not only chromium phosphate but also a phosphate of Group 2 element is formed in the film, which is difficult to dissolve in water. Further, when chromium was replaced with aluminum, the conventional finishing treatment liquid composition did not provide any improvement in corrosion resistance, but in the present invention, the addition of the second group element showed an improvement in corrosion resistance, Sufficient performance was obtained as a non-chrome finish. It can be presumed that this is also the effect that the aluminum salt of the second group element is generated and is difficult to dissolve in water.

  The present invention will be described in detail. In the finishing treatment liquid of the present invention, trivalent chromium and aluminum are used alone or in combination, and their total concentration is 0.2 to 50 g / L, preferably 0.5 to 20 g / L. When it is less than 0.2 g / L, the corrosion resistance is lowered, and when it is more than 50 g / L, the effect reaches a peak and is inefficient. Examples of the trivalent chromium source include trivalent chromium salts such as chromium chloride, chromium nitrate, chromium sulfate, chromium (III) phosphate, and chromium acetate, and hexavalent chromium such as chromic acid and dichromic acid using a reducing agent. One or more of trivalent chromium reduced to a valence can be used. As the aluminum source, trivalent aluminum salts such as aluminum chloride, aluminum nitrate, aluminum sulfate, aluminum phosphate and aluminum acetate can be used.

  As a source of phosphorus oxygen acid, in addition to chromium (III) phosphate, aluminum phosphate, a kind of phosphoric acid compound group consisting of orthophosphoric acid, condensed phosphoric acid, phosphorous acid, hypophosphorous acid and salts thereof Although the above is possible, it is not limited to this. The content of phosphorus oxyacid ions in the finishing agent may be an excess equivalent to the total of chromium (III) ions and aluminum ions.

  Sources of the second group elements include, but are not limited to, metal salts such as Mg, Ca, Sr, Ba sulfate, nitrate, chloride, acetate, and the like. The concentration of the second group element is preferably 0.1 to 5 times the total concentration of chromium and aluminum, more preferably 0.5 to 3 times, and still more preferably 0.8 to 2 times. If it is less than 0.1 times, the corrosion resistance improving effect cannot be obtained. If it exceeds 5 times, precipitation is likely to occur, and the effect is limited and inefficient. Among the Group 2 elements, Ca is suitable in terms of the effect of improving the corrosion resistance.

  A substance having chelating properties can be added to the finishing solution of the present invention for the purpose of improving stability and preventing precipitation. Examples thereof include monocarboxylic acid, polyvalent carboxylic acid, aliphatic amine, aliphatic polyamine, and salts thereof. Of these, polyvalent carboxylic acids or their salts, particularly oxalic acid, succinic acid, malonic acid, citric acid or their salts are preferred. Examples of monocarboxylic acids include formic acid and acetic acid, examples of aliphatic amines include triethanolamine, and examples of aliphatic polyamines include, but are not limited to, polyethyleneimine. The concentration is preferably 1 to 100 g / L, more preferably 5 to 50 g / L.

  The finishing solution of the present invention can further contain one or more selected from the group consisting of metal ions, metal oxide ions, and silicon compounds other than those described above.

  Such metal ions are preferably Co, Ni, and Zn, and can be supplied in the form of an inorganic metal salt such as cobalt sulfate, nickel chloride, and zinc nitrate, but is not limited thereto. The metal ion concentration is preferably 0.01 to 50 g / L, more preferably 0.05 to 20 g / L.

  The metal element of the metal oxide ion is preferably Mo, W, or V, and is supplied by a metal oxyacid or a salt thereof that generates molybdate, tungstate, or vanadate ions. Although there is no limitation of a cation, there exist a sodium ion, a potassium ion, an ammonium ion etc., for example. The metal oxide ion concentration is preferably 0.01 to 50 g / L, more preferably 0.05 to 20 g / L.

  The silicon compound is not intended to be limited, but includes potassium silicate, sodium silicate, lithium silicate, colloidal silica (preferably having a particle size of 500 nm or less), and the silicon concentration is 0.01 to It is preferable that it is 50 g / L, More preferably, it is 0.05-20 g / L.

  There is no particular limitation on the chemical conversion film to which the finishing treatment is applied. As the trivalent chromium chemical conversion film, for example, those described in Japanese Patent No. 3392008 and Japanese Patent No. 3332373 can be used. The color tone of the chemical conversion film is generally classified into colorless, colored, black and the like, but is not particularly limited to this classification.

  The non-chromium chemical conversion film is not intended to be limited, but examples thereof include a vanadium chemical conversion film formed by immersing a base material subjected to zinc plating in an aqueous solution of vanadate and cerium salts.

  Although there is no particular limitation on the material of the object on which the chemical conversion film capable of finishing according to the present invention is applied, examples thereof include zinc, copper, nickel, silver, iron, cadmium, aluminum, magnesium, and alloys thereof. If necessary, plating treatment such as galvanization may be performed. There is no particular limitation on the shape of the object. For example, fastening parts such as bolts, washers and nuts can be mentioned.

  Although not intended to be limiting, an example of how to use the finish according to the present invention will be described. The surface of the galvanized iron part is coated with a chemical conversion film not containing hexavalent chromium, washed with water, and then brought into contact with the finish of the present invention. The contact method may be shower or dipping, and dipping is preferred. After contact, it is dried at 30 to 200 ° C., preferably 40 to 120 ° C., for 2 to 30 minutes, preferably 5 to 15 minutes.

  In addition, after the above treatment, silicon compound, resin, inorganic colloid, silane coupling agent, organic carboxylic acid, thiazole, triazole, amine compound, caustic alkali, ammonia, phosphorus oxyacid, PVA, nonionic polymer, A protective film forming method can be performed in which a solution having at least one selected from the group consisting of polyol, cellulose, polyacrylic acid, acid amide compound, fatty acid ester, thiol compound, tannic acid and mercapto group is contacted. There is no particular limitation on the processing conditions for this protective film forming method.

  Examples carried out to confirm the effects of the present invention will be described. First, after performing appropriate pretreatments such as degreasing and acid soaking of the test piece, galvanization (Hyper Zinc; Nippon Surface Chemical Co., Ltd.), zinc iron alloy plating (Stron Zinc; Nippon Surface Chemistry Co., Ltd.), One of zinc-nickel alloy plating (Stron Ni zinc; Nippon Surface Chemical Co., Ltd.) was applied. Subsequently, nitric acid immersion was performed as necessary, and then the chemical conversion film treatment shown below was performed. Thereafter, the test piece was taken out of the treatment liquid and washed with water. And the test piece was immersed in the aqueous solution (finishing agent) which has a composition of the following Table 1-1-Table 5-2 on the process conditions as described in the same table, and the finishing process was performed. The test piece used was an iron M8 bolt, washer, nut, and iron plate (50 mm × 100 mm, thickness 1 mm). The thickness of the plating was 8 to 10 μm for any plating.

  Chemical film treatment is (1) on zinc plating, trivalent chromium colored chemical film treatment is on Triner TR-173A (manufactured by Nippon Surface Chemical Co., Ltd.), (2) on zinc iron alloy plating, trivalent chromium colored chemical film treatment 5S071AB (manufactured by Nippon Surface Chemistry Co., Ltd.), (3) on zinc-nickel alloy plating, trivalent chromium colored chemical film treatment is on Triner TRN-988AC (manufactured by Nippon Surface Chemistry Co., Ltd.), (4) on zinc plating, Trivalent chromium black chemical conversion film treatment is Triner TR-185FG (manufactured by Nippon Surface Chemical Co., Ltd.), (5) Trivalent chromium black chemical conversion film treatment is triner TRF-966AB (Nihon Surface Chemicals Co., Ltd.) (6) On the zinc-nickel alloy plating, the trivalent chromium black chemical conversion film treatment was performed using 5W115 (manufactured by Nippon Surface Chemical Co., Ltd.). (7) On galvanizing, non-chromic conversion coating treatment is an aqueous solution of vanadium iodide 2 g / L, cerium (III) chloride 10 g / L, 25% titanium sulfate 6 g / L, zirconium nitrate 3 g / L, 30 ° C., pH 2.0 For 60 seconds.

ここで、Ｐ：ネジのピッチ、ｄｅ：ネジの有効径、ｄＮ：座面等価直径、ｃｏｓα：リード角。
なお外観は○が均一性が高い、△は均一性にやや劣る、×は外観不良である。 The results are shown in Table 1-1 to Table 5-2. The external appearance was evaluated visually, and the corrosion resistance was evaluated by white rust 5% generation time in a salt spray test (JIS Z 2371). Bolts, washers and nuts were used as test pieces for measuring the coefficient of friction during fastening. This friction coefficient (μ) is calculated by measuring torque (T) and axial force (Q) generated when fastening bolts, washers and nuts, and applying them to Equation 1.

Here, P: screw pitch, de: effective screw diameter, dN: bearing surface equivalent diameter, cos α: lead angle.
In addition, as for appearance, ○ is highly uniform, Δ is slightly inferior in uniformity, and × is poor appearance.

Comparative Examples 9-11:
On the same trivalent black chemical conversion film as in Comparative Example 1, an overcoat was applied using GX-235T (manufactured by Nippon Surface Chemistry Co., Ltd .: water-soluble acrylic resin). The relationship between the concentration and the coefficient of friction at that time, the uniformity of appearance, and the ease of drying of the film is as shown in Table 6 below, and the overall coefficient of friction is greatly reduced regardless of the concentration of the overcoat treatment liquid. Uniformity was visually determined, and easiness of drying was judged in a dry state after drying at 60 ° C. for 5 minutes. Each of the finishing treatments of Examples 1 to 24 is significantly improved in corrosion resistance as compared with Comparative Examples 1 and 3, and is excellent in that the change in the friction coefficient due to the presence or absence of the finishing treatment is small as compared with Comparative Examples 9 to 11. Yes.

Claims (11)

  (A) One or more selected from chromium (III) ions and aluminum ions in total 0.2 to 50 g / L, (B) phosphorus oxyacid ions, and (C) Mg, Ca, Sr and Ba A finishing agent for a chemical conversion film that does not contain hexavalent chromium, containing 1 g / L or more of at least one selected ion.   Furthermore, the finishing agent of Claim 1 containing the substance which has chelating property.   The finishing agent according to claim 1 or 2, which contains an excess equivalent amount of phosphorus oxyacid ions relative to the total of chromium (III) ions and aluminum ions.   Furthermore, 1 or more types selected from the group which consists of metal ions other than the metal of Claims 1-3, a metal oxide ion, and a silicon compound are contained, The any one of Claims 1-3 characterized by the above-mentioned. Finishing agent described in 1.   The finishing agent according to claim 4, wherein the metal ion other than the metal according to any one of claims 1 to 3 is at least one selected from Co, Ni and Zn.   The finishing agent according to claim 4 or 5, wherein the metal element of the metal oxide ion is one or more selected from Mo, W and V.   The finish according to any one of claims 4 to 6, wherein the silicon compound is at least one selected from sodium silicate, potassium silicate, lithium silicate, and colloidal silica.   A finishing treatment method for a chemical conversion film using the finishing agent according to any one of claims 1 to 7.   After the finishing treatment according to claim 8, the silicon compound, resin, inorganic colloid, silane coupling agent, organic carboxylic acid, thiazole, triazole, amine compound, caustic, ammonia, phosphorus oxyacid, PVA, non- Protective film to be contacted once or a plurality of times with a solution having at least one selected from the group consisting of ionic polymer, polyol, cellulose, polyacrylic acid, acid amide compound, fatty acid ester, thiol compound, tannic acid and mercapto group Forming method.   The component in which the chemical conversion film that has been subjected to the finishing treatment using the treatment method according to claim 8 or 9 is formed on zinc, copper, nickel, silver, iron, cadmium, aluminum, magnesium, or an alloy thereof. .   The component according to claim 10, wherein the metal is zinc or a zinc-based alloy.