JP4846988B2 - Finishing agent for chemical conversion film containing no hexavalent chromium - Google Patents

Description

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

  In addition to improving the rust prevention and paint adhesion on the surface of zinc, copper, nickel, silver, iron, cadmium, aluminum, magnesium and their alloys, there is a surface treatment method. Brings design and so on. One of them is chromate treatment containing hexavalent chromium. This is a technique for imparting so-called rust prevention by applying a chromate film on the surface of zinc and zinc-based alloy plating (hereinafter referred to as zinc plating), and is generally most widely used for iron-based materials and parts. Recently, technological development of chemical conversion coatings that do not use hexavalent chromium, that is, hexavalent chromium replacement coatings has been actively conducted from the viewpoint of the environment. Combined with overcoat technology that applies organic film such as acrylic resin, methacrylic resin, fluorine resin, urea resin, phenol resin, alkyd resin, melamine resin, epoxy resin and inorganic film such as silicate and phosphate This is described, for example, in Japanese Patent No. 3332373. Other features of the overcoat include uniforming the color tone of the chemical conversion film, imparting gloss, and preventing damage between parts.

Japanese Patent No. 3332373

  However, organic coatings and inorganic coatings used for overcoats are viscous, and it is difficult to uniformly apply these coatings to parts or to dry them. For example, In cup-shaped parts, it takes time for the coating agent to flow down and become uniform, a so-called pool where the coating agent stays on the part occurs, the coating agent stays in the part where the parts hit each other, In the drying process, the accumulation or staying portion of the coating agent is left as it is, or the coating agent is dried and becomes a stain while the coating agent is flowing down.

  In addition, fastening parts such as bolts, washers, and nuts are required to have a friction coefficient equivalent to that of current chromate as well as rust prevention. For example, when tightened with a constant torque, if the friction coefficient is high, the bolt itself will be strongly stressed and will be damaged, and if the friction coefficient is low, the bolt will loosen. is required. However, when overcoating with an organic coating agent, the coefficient of friction is significantly reduced because the slipperiness of the organic coating is good.

  Due to these difficulties, the yield does not increase and the parts that can be overcoated are limited, so that productivity is lowered, and if better equipment is introduced, there is a concern that the number of processing steps increases and the production cost increases. On the other hand, finishing agents that have the same purpose as the overcoat and that do not have the above-mentioned problems are considered effective, but so far there are no finishing agents that can be used after applying a conversion coating that does not contain hexavalent chromium. .

Therefore, an object of the present invention is to solve the above problems. More specifically, it improves the rust prevention, uniformity of color tone, and gloss of conversion coatings, especially conversion coatings that do not contain hexavalent chromium applied to the surface of galvanized iron parts, and may occur in overcoats. The object of the present invention is to provide a finishing agent that can be applied to a fastening part without any problem of accumulation or friction coefficient and the shape of an object is not limited.
In addition, in this specification, in order to distinguish with the conventional overcoat agent, the chemical conversion film processing agent by this invention is called a "finishing agent."

  In order to overcome the above-mentioned problems, the present inventors have intensively studied for a substance that gives a desired rust prevention property, etc. even though it does not form a thick film like an overcoat. It has been found that the intended purpose can be achieved with a finish having characteristics.

  That is, the present invention is a finish for a chemical conversion film characterized by containing phosphorus oxyacid ions and chromium (III) ions.

  In one embodiment of the present invention, chromium (III) phosphate is used as a supply source of the phosphorus oxyacid ion and chromium (III) ion.

  Moreover, in one Embodiment of this invention, the density | concentration of chromium (III) phosphate contained in a finishing agent is 0.01-10 g / L.

  In addition, the finishing agent of the present invention contains, in one embodiment, an excess equivalent amount of phosphorus oxyacid ion to chromium (III) ion.

  In one embodiment of the present invention, the phosphorus oxyacid ion is one or two selected from the group consisting of orthophosphoric acid, condensed phosphoric acid, phosphorous acid, hypophosphorous acid, and salts thereof. Supplied from more than seeds.

  In one embodiment, the finishing agent of the present invention further contains at least one selected from the group consisting of metal ions, metal oxide ions, carboxylic acids and salts thereof, and silicon compounds.

  Moreover, in one Embodiment of this invention, the said chemical conversion film is produced | generated from the process liquid which does not contain hexavalent chromium of pH 0.1-6.5.

  Moreover, in one Embodiment of this invention, the said metal ion is 1 type, or 2 or more types selected from the group which consists of Co, Ni, Mg, and Ca.

  Moreover, in one Embodiment of this invention, the metal element of the said metal oxide ion is 1 type, or 2 or more types selected from the group which consists of Mo, W, and V.

  Moreover, in one Embodiment of this invention, the said carboxylic acid and its salt are 1 type (s) or 2 or more types selected from the group which consists of oxalic acid, malonic acid, succinic acid, and these salts.

  In one embodiment of the present invention, the silicon compound is one or more selected from the group consisting of sodium silicate, potassium silicate, lithium silicate, and colloidal silica.

  Moreover, in one Embodiment of this invention, the viscosity of a finishing agent in 25 degreeC is 0.5-10 cps.

Moreover, in one Embodiment of this invention, the said chemical conversion film is given to the surface of the iron component which gave zinc or zinc alloy plating, and the said iron component after a finishing process is also contained in another embodiment of this invention.
Furthermore, this invention is zinc, copper, nickel, silver, iron, cadmium, aluminum, magnesium, or these alloys which performed the finishing process of the chemical conversion film using the said finishing agent in one Embodiment.

According to the present invention, it is possible to improve the rust prevention, uniformity of color tone, and gloss of a chemical conversion film, particularly a chemical conversion film not containing hexavalent chromium applied to the surface of a galvanized iron part, and with an overcoat. Since there is no problem of the accumulation and friction coefficient that occur, the shape of the object is not limited, and a finish that can be applied to fastening parts can be provided.
As a result, fluctuations in the number of processing steps depending on the part shape, etc. that were unavoidable when performing overcoat processing, can be suppressed, contributing to reductions in process remodeling and maintenance costs, as well as production costs. it can.

  The present inventors have prepared a finishing agent using chromium (III) phosphate, chromium (III) chloride, chromium (III) nitrate, chromium (III) sulfate, orthophosphoric acid, condensed phosphoric acid, phosphorous acid. As a result of a comparative experiment of finishing agents combining at least one of phosphoric acid compound groups consisting of acid, hypophosphorous acid, and salts thereof, an interesting behavior was found for the finishing agent of chromium (III) phosphate. First of all, a zinc plating is applied to an iron plate (5 cm x 10 cm), a chemical conversion film not containing hexavalent chromium is applied, washed with water, then dipped in a finish of chromium (III) phosphate and dried, and then a salt spray test As a result of performing (JIS Z 2371), it was found that the rust prevention property was remarkably improved. Second, the addition of metal ions, metal oxide ions, phosphorus oxyacids and salts, carboxylic acids and salts, and silicon compound metal ions to chromium (III) phosphate finishes further improves rust prevention. It was found that the color tone of the chemical conversion film was made uniform and the gloss was improved.

The reason for this result is not clear, but the basic chromium (III) phosphate finish forms a kind of very thin phosphate film that does not reach the thickness of the conversion film. It is assumed that the surface of the chemical conversion film is modified. In addition, the finishing agent has a lower viscosity than the organic or inorganic coating agent used for overcoating, and the concentration of each component of the finishing agent is low, so there is no trace of accumulation or stains, and the shape of the part. Because it can be used regardless of productivity, productivity is not reduced. The viscosity of organic coatings and inorganic coatings usually used for overcoats is 10 to 500 cps at 25 ° C., and a concentration that functions as an overcoat is required, and the concentration is 20 to 500 g / L. On the other hand, the viscosity of the finishing agent of the present invention is 0.5 to 10 cps, preferably 0.8 to 8 cps, more preferably 1 to 5 cps at 25 ° C. The concentration of each component is as shown below. Such a low concentration and low viscosity composition is usually unthinkable, such as providing rust prevention or the like comparable to or higher than that of the overcoat.
Addition of metal ions, metal oxide ions, phosphorus oxyacids and salts thereof, carboxylic acids and salts thereof, and silicon compound metal ions to finishes containing chromium (III) phosphate It is presumed that the water-repellent effect appeared because the surface of the chemical conversion film was made smooth because it contributed to further improvement.

  Each configuration of the above means will be described in detail below.

  The method for supplying chromium (III) phosphate used in the finishing agent of the present invention includes (A) an aqueous solution of solid chromium (III) phosphate, (B) hexavalent chromium compound, phosphorous acid, hypophosphorous acid. 1 selected from the group consisting of normal phosphoric acid, condensed phosphoric acid, and salts thereof of chromium (III) phosphate and (C) hexavalent chromium compound formed by reduction with a phosphoric acid compound comprising an acid or a salt thereof. Chromium (III) phosphate, (D) hexavalent chromium formed by dissolving in an aqueous solution containing at least one type of phosphoric acid compound and reducing with a phosphoric acid compound consisting of phosphorous acid, hypophosphorous acid and salts thereof The compound is dissolved in an aqueous solution containing at least one phosphoric acid compound selected from the group consisting of orthophosphoric acid, condensed phosphoric acid, phosphorous acid, hypophosphorous acid, and salts thereof to form hydrazine hydrate, Reduced with organic substances such as acid and methanol There chromic phosphate (III), but is not limited thereto. (A) Since solid chromium (III) phosphate is insoluble in water, one or more types of phosphorus selected from the group consisting of normal phosphoric acid, condensed phosphoric acid, phosphorous acid, hypophosphorous acid and salts thereof Used by dissolving in an aqueous solution containing an acid compound. It is important that the chromium phosphate produced by reducing the hexavalent chromium compound as in (B) to (D) is not detected by the diphenylcarbazide method or the like. As the hexavalent chromium compounds (B) to (D), chromate, dichromate, and chromium oxide can be used, and among them, chromium oxide that can be easily supplied at low cost is optimal. The concentration of chromium (III) phosphate is preferably 0.01 to 10 g / L, more preferably 0.05 to 8 g / L, and most preferably 0.1 to 5 g / L.

  The metal ions are preferably Co, Ni, Mg, and Ca, and can be supplied in the form of inorganic metal salts such as cobalt sulfate, nickel chloride, magnesium nitrate, and calcium chloride, but are not limited thereto. These metal ion concentrations are preferably 0.001 to 1 g / L, more preferably 0.05 to 0.75 g / L, and most preferably 0.1 to 0.5 g / L.

  The metal element of the metal oxide ion is preferably Mo, W, or V, and is supplied by, for example, 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 0.001 to 1 g / L, more preferably 0.05 to 0.75 g / L, and most preferably 0.1 to 0.5 g / L.

  Phosphorus oxyacid ions are not intended to be limiting, but may be supplied from orthophosphoric acid, condensed phosphoric acid, phosphorous acid, hypophosphorous acid and their salts (eg, sodium hypophosphite), etc. The concentration of oxygenate ions is preferably 0.001 to 1 g / L, more preferably 0.05 to 0.75 g / L, and most preferably 0.1 to 0.5 g / L.

  Carboxylic acids and salts thereof include, but are not intended to be limited to oxalic acid, malonic acid, succinic acid, and alkali metal salts or alkaline earth metal salts thereof, specifically potassium oxalate, malonic acid. Examples thereof include sodium and sodium succinate, and the concentration is preferably 0.001 to 1 g / L, more preferably 0.05 to 0.75 g / L, and most preferably 0.1 to 0. 5 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 concentration is 0.001 to 1 g. / L, more preferably 0.05 to 0.75 g / L, and most preferably 0.1 to 0.5 g / L.

  The pH of the treatment liquid for producing a chemical conversion film containing no hexavalent chromium is preferably 0.5 to 6.5, more preferably 1 to 6, because it is an acidic region where the film is formed. Although not intended to be limited, the chemical conversion film described in Japanese Patent No. 3392008 and Japanese Patent No. 3332373 may 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.

  Objects to which the conversion coating capable of finishing according to the present invention is applied include, but are not limited to, zinc, copper, nickel, silver, iron, cadmium, aluminum, magnesium, and alloys thereof. These may be subjected to a plating treatment such as galvanization as necessary. Among these, the present invention is particularly preferably used for iron parts subjected to galvanization. The present invention can be used regardless of the shape of the object, and is not intended to be limited. For example, in addition to fastening parts such as bolts, washers, and nuts, flat plate pressed parts and parts Of course, it can also be used for brazed parts, straight pipe parts processed into a cylindrical shape, or parts formed with a straight pipe.

  The present invention is preferably used as a finishing agent for a conversion coating not containing hexavalent chromium for the purpose of reducing the load on the environment and the human body, and for the same purpose, the conversion coating is applied to the surface of a galvanized iron part. It is particularly preferred.

  The friction coefficient when fastening bolts, washers, and nuts that have been finished using the finish of the present invention is comparable to that of current chromate.

An example of the method of using the finish of the present invention will be described. The surface of the galvanized iron part is coated with a chemical conversion film containing no hexavalent chromium, washed with water, and then containing 5 to 40 ° C., preferably 10 containing chromium (III) phosphate as a finishing agent of the present invention. The solution is brought into contact with an aqueous solution having a pH of 2 to 6, preferably 3 to 5 at -30 ° C for 2 to 60 seconds, preferably 10 to 30 seconds. Examples of the contact method include shower and immersion, and immersion is preferable. Thereafter, the part is taken out from the aqueous solution and dried at 30 to 200 ° C., preferably 40 to 120 ° C. for 2 to 30 minutes, preferably 5 to 15 minutes, to finish the part.
The overcoat is intended to completely cover the surface of the object to be processed, and in some cases, may be repeatedly dipped and dried during the process. The accompanying increase in cost is inevitable.

  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 Zincate; Nihon Surface Chemical Co., Ltd.), zinc iron alloy plating (Strong Zinc; Nihon Surface Chemistry Co., Ltd.), One of zinc-nickel alloy plating (Stron Ni zinc; Nippon Surface Chemical Co., Ltd.) was applied. Then, if necessary, after nitric acid immersion, the test piece is immersed in an aqueous solution having a composition as shown in Table 1 under the treatment conditions described in the same table to perform a chemical conversion film treatment, and then the test piece is taken out from the treatment solution. And washed with water. And the test piece was immersed in the aqueous solution (finishing agent) which has a composition like the same table on the process conditions as described in the same table, and the finishing process was performed. For the test piece, iron M10 bolts, washers, nuts, and iron plates (50 mm × 100 mm, thickness 1 mm) were used. The plating film thickness was 8 to 10 μm in any plating.

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。 The appearance was evaluated visually, and the rust prevention property was evaluated from the results of a salt spray test (JIS Z 2371) after 120 hours. Bolts, washers, and nuts were used as test pieces for measuring the friction coefficient at the time of 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 Examples 1 to 8, the iron plate was plated with zinc, zinc-iron alloy, or zinc-nickel alloy to form a chemical film, and then finished with a finish containing chromium (III) phosphate to prevent appearance and prevention. Rust was evaluated. In Example 9, after galvanizing iron bolts, washers, and nuts, finish treatment with a finish containing chromium (III) phosphate was performed to evaluate the appearance and rust prevention, and the friction coefficient at the time of fastening was determined. It was measured. In addition, Snowtex S in Example 7 is crocodile silica containing 20 to 21% by weight of SiO ₂ manufactured by Nissan Chemical Industries, Ltd.

  Referring to Table 2, Comparative Examples 1 to 3 were obtained by applying a chemical conversion film by galvanizing an iron plate, and then finishing with no finishing treatment (Comparative Example 1) and an aqueous solution of chromium (III) sulfate (Comparative Example 2). And finished with only an aqueous solution of phosphoric acid (Comparative Example 3). In Comparative Example 4, a steel film was coated with GX-235T (manufactured by Nippon Surface Chemistry Co., Ltd .: water-soluble acrylic resin) without applying a finish after zinc plating was applied to iron bolts, washers and nuts. It is. In Comparative Example 5, after galvanizing iron bolts, washers and nuts and applying commercially available chromate (MB-343: manufactured by Nippon Surface Chemical Co., Ltd.), RB-775 (manufactured by Nippon Surface Chemicals Co., Ltd .; black) Hexavalent chromate finish).

  As apparent from Table 3, the finish of the present invention provides a uniform and glossy appearance, improves rust prevention, and has a friction coefficient comparable to that of the current chromate. And it turns out that rust prevention property is improving by adding a metal ion, a metal oxide ion, carboxylic acid, a silicon compound, etc. other than chromium (III) phosphate as a component of the finishing agent of this invention.

Claims (9)

A finishing agent for a trivalent chromium conversion coating that does not contain hexavalent chromium,
The trivalent chromium chemical conversion film is a trivalent chromium chemical conversion film applied to the surface of an iron part subjected to zinc or zinc alloy plating,
Contains phosphorus oxyacid ions and chromium (III) ions,
Using at least 0.01 to 10 g / L of chromium (III) phosphate as a source of oxygen ions and chromium (III) ions of phosphorus,
In addition, it contains metal oxide ions,
The metal element of the metal oxide ion is Mo,
pH is 3-5, viscosity at 25 ° C. is 1-5 cps,
A finishing agent for a trivalent chromium chemical conversion film containing no hexavalent chromium, having a composition different from that of the treatment liquid used for forming the trivalent chromium chemical conversion film.   The finish according to claim 1, further comprising at least one selected from the group consisting of metal ions, carboxylic acids and salts thereof, and silicon compounds. The finishing agent according to claim 1 or 2 , which contains an excess equivalent amount of phosphorus oxyacid ion to chromium (III) ion. The oxyacid ion of the phosphorus is supplied from one or more selected from the group consisting of orthophosphoric acid, condensed phosphoric acid, phosphorous acid, hypophosphorous acid and salts thereof. Item 4. A finishing agent according to any one of Items 3 to 4 . The finishing agent according to any one of claims 2 to 4 , wherein the metal ion is one or more selected from the group consisting of Co, Ni, Mg, and Ca. The said carboxylic acid and its salt are 1 type (s) or 2 or more types selected from the group which consists of an oxalic acid, malonic acid, a succinic acid, and these salts, It is any one of Claims 1-5 Finishing agent. The finish according to any one of claims 1 to 6 , wherein the silicon compound is one or more selected from the group consisting of sodium silicate, potassium silicate, lithium silicate, and colloidal silica. Agent. The iron component which performed the finishing process of the trivalent chromium chemical conversion film using the finishing agent as described in any one of Claims 1-7. The iron part according to claim 8 , wherein the part is a fastening part.