JP2994428B2 - Composition for treating phosphate film and treatment method - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an improved method of forming a zinc phosphate-containing protective coating on the surface of iron, steel and other metal products. Such a layer, when sufficiently uniform and dense, provides an effective base for lubrication in subsequent drawing or similar metal forming operations. More specifically, the present invention relates to processing solution compositions and methods that reduce the amount of sludge formed during the phosphating step.

[Prior Art and Problems to be Solved by the Invention] Metal phosphating solutions have been widely used for forming a film on the surface of a metal product, particularly a product made of iron and carbon steel. Metal phosphating solutions are generally aqueous solutions of phosphoric acid and other chemical agents, and include zinc, calcium,
And other metal ions, which are brought into contact with the metal surface by dipping, spraying or similar means. The surface of the metal reacts with the solution and under suitable conditions, the reaction presents various metals on the metal surface, usually iron (if this is part of the metal to be phosphatized), and in solution. An integral layer of substantially insoluble crystalline phosphate containing metal is formed.

The film formed in this way serves as an effective base when applying paints, lubricants, and other substances in a later stage. In addition, many of such films have corrosion resistance, and in various environments where metal products are frequently exposed during use, corrosion of the metal under the film is suppressed. Such coatings have hitherto been widely used commercially.

One particular area where the use of phosphate coatings has been established,
There are areas in which metals are pretreated for drawing and similar forming operations, in which it is important to reduce surface friction. In such applications,
It has been established that phosphating solutions containing both zinc and calcium ions are superior to most if not all. For example, US Pat. No. 4,688,411 issued Aug. 25, 1987 to Hagita et al.
It is taught to use a mixed phosphating solution of calcium and zinc of 0.3-1 at 70-90C. As shown in Table 4 of this Hagita patent, the greater the calcium / zinc ratio, the more specific non-z
ero) The film weight achieved in the processing time is smaller.

The use of hydroxyamine in phosphating solutions
It is known as a technique for accelerating the phosphating reaction, whereby a phosphating solution containing hydrosylamine can give a given phosphating solution under given processing conditions compared to a similar solution containing no hydroxylamine. The amount of phosphate film formed increases.

All known phosphating solutions, in addition to their desired effects, generate during use of undesirable substances commonly known in the art as "sludge". This sludge is an insoluble mixture of metal phosphate and possibly other substances that precipitate from the phosphating solution during use and must be removed from the system in order to continue satisfactory processing. It must be. If the sludge accumulates above a certain concentration level, a portion of the sludge will normally adhere to some of the phosphated metal articles, causing these products to have very unacceptable surface stains. The disposal of sludge is costly because of the high concentrations of harmful metal ions and under current legislation it is necessary to take environmental protection measures.
Therefore, reducing the amount of sludge generated during processing is a highly desirable improvement in phosphating processes.

[Means for Solving the Problems] First, except for the cases described in the embodiments or explicitly stated otherwise, all figures in the present specification indicating the amounts of substances or reaction conditions or use conditions are as follows: In all cases, it is to be understood that the term is modified by the word "about".

In view of the above problems, the present invention provides an aqueous solution for phosphating a metal surface having a pH in the range of 1 to 3.7, and (A) at least 1% by weight of zinc ions;
(B) at most 3% by weight of calcium ions, (C) at least 1% by weight of phosphate ions, (D) at least 0.02% by weight of hydroxylamine, (E) an amount of an accelerator other than hydroxylamine, which effectively works as an accelerator. And (F) containing up to 0.1% by weight of nickel and / or copper ions, and a method for phosphating the metal by contacting the aqueous composition with the metal.

According to this, in order to obtain the lubricating properties required for drawing work satisfactorily with a phosphate coating, the phosphate coating should be 3 to 15 grams per square meter of surface (hereinafter "g / m ² "). This means that the coating can be carried out by forming the film in the range of the film weight.If a dense continuous phosphate film is formed, the film weight of the lower value in the above range may be preferable. It is. further,
The controlled addition of hydroxylamine to the zinc phosphating solution can significantly reduce sludge formation during processing without any adverse effect on the phosphating step. Incidentally, the above-mentioned solution also includes a solution containing calcium and / or other metal ions.

One of the preferred embodiments of the present invention is a phosphating solution having a pH in the range of 1 to 3.7, more preferably 2.5 to 3.5, and comprising the following components, or more preferably:
It consists essentially of the following components: Here, the following components are (A) 1 to 4% by weight of zinc ion, (B) maximum 3% by weight of calcium ion, (C) 1 to 7.5% of phosphate ion.
% By weight, (D) at least 0.02% by weight of hydroxylamine, (E) a known accelerator other than hydroxylamine,
The chemical species may be one or more, but it contains an effective amount of an accelerator and (F) up to 0.1% by weight of nickel and / or copper ions, and further up to 0.2% by weight of manganese ions. % Can be included. In the definition of the above components and the rest of the specification,
The amount of "phosphate ions", shall be understood to a respective stage and stoichiometrically equivalent amount of PO ₂ ^-3 the sum of undissociated acid that may be present in the solution of ions of phosphoric acid And It is also understood that, for those components which are stated to be present in ionic form, the corresponding ions which are naturally present and which are chemically harmless during the phosphating step are also present in the solution according to the invention. Shall be.

A preferred accelerator is nitrate, the amount of which is 1 to 7.5% by weight. Other suitable accelerators include, but are not limited to, sulfite, picrate, vanadate, and / or molybdate.

Within the above-mentioned component ranges, the amount of nickel ions and / or copper ions should be between 0.001 and 0.01% by weight, more preferably 0.006% by weight. Preferably, the calcium ions are present in a concentration of at least 0.5% by weight.

When all of the hydroxylamine in the phosphating solution of the present invention was subjected to the chemical conversion treatment on the metal surface with a phosphating solution in which an amount of nitrite ion was replaced by a normal chemical conversion film, the treatment was performed with the treating solution of the present invention. It was found that more than 50% more sludge was generated.

The amount of hydroxylamine used in the present invention is 0.4% by weight
The following is preferable, and a more preferable amount is 0.05% by weight.

The treatment of metal surfaces with the hydroxylamine-containing phosphating solutions of the present invention can be carried out by dipping, spraying, combinations thereof, or any other method that provides effective contacting. The time, time, and other conditions are generally the same as known techniques for phosphating with solutions containing the same metal ions and other accelerators (including multiple accelerators) at the same concentration. It may also be advantageous to use the phosphating of the present invention in accordance with known general methods in combination with other known methods and steps. These known methods and steps include washing, pickling, and surface conditioning steps prior to phosphating, post-treatment by chromating or other passivating treatments, application of lubricants, painting, and the like.

Suitable, practical and preferred sources for specific components of the phosphating solution of the present invention are known to those skilled in the art. For example, hydroxylamine is preferably obtained from storage-stable salts or complexes, some of which are commercially available. Most preferred is the sulfate of hydroxylamine, also referred to as hydroxylammonium sulfate, which is generally chemically identified as (NH ₂ OH) ₂ · (H ₂ SO ₄ ) or (NH ₃ OH) ₂ SO ₄ Is shown. This hydroxylammonium sulfate will be simply referred to as "HAS" below.

The amount of sludge generated during use of the phosphating solution can be measured by methods known to those skilled in the art. Usually, a fixed volume sample is collected from the tank in which the treatment is being performed. At this time, care must be taken to take a representative sample. The collected solution has suspended solids,
This is transferred to a transparent graduated cylinder and allowed to settle under the influence of ambient gravity for about 24 hours. This settling gives rise to an easily visible parting line between the sludge at the bottom of the cylinder and the liquid above it. Next, the volume of the sludge is read from the scale of the measuring cylinder.

With typical phosphate treatment solution of the present invention, metal- 1 square meter is phosphated (hereinafter referred to as "m ^2") (hereinafter referred to as "m") per 7-11 ml of sludge is generated for. On the other hand, when the conventional zinc phosphate treatment liquid is used, 14 to 25 m / m ^{2 of the} phosphate-treated metal is used.
Sludge is generated.

EXAMPLES The practice of the present invention will be better understood in view of the following non-limiting examples.

Examples 1 to 5 These examples illustrate the preparation and use of the phosphating solution of the present invention. These solutions were prepared so as to have the compositions shown in Table 1. Here, zinc oxide was used as a source of zinc, nitric acid was used as a source of nitrate ions, phosphoric acid was used as a source of phosphate ions, and hydroxide was used. Calcium was used as a source of calcium ions, nickel nitrate was used as a source of nickel ions, and HAS was used as a source of hydroxylamine. Some of the results using these solutions are shown in Table 2.

Examples 7-8 and Comparative Examples 1C-3C The compositions of the solutions in these examples are shown in Table 3. Using the same composition source as in Examples 1 to 6, sodium nitrite was used as a source of nitrite ions.

All comparative examples are solutions known from the prior art. Comparative Example 1C is a traditional zinc solution for high film weight phosphating, and 2C is a conventional solution for low film weight phosphating, both solutions containing no calcium. Comparative Example 3C contains calcium but is otherwise close to 1C. All of these comparative examples contain nitrite as promoter along with nitrate.

Some of the results obtained with these solutions are shown in Table 4. In Example 8, the same solution as that of Comparative Example 3C was used, except that the hydroxylamine in the solution of Example 8 was replaced with nitrite ion in Comparative Example 3C. The amount is 3% by weight of the amount of substituted hydrosylamine. The phosphating film weight and quality obtained from these two solutions are substantially the same,
The amount of sludge in Example 8 is 40% less. Comparative Example 1C
Comparing Example 7 with Example 7, it is shown that a solution with a high zinc / calcium ratio has the same general effect.

Example 9 This example illustrates the overall process involving the use of the phosphating solution of the present invention, which is used to prepare a steel pipe or wire for subsequent drawing or cold working. Extremely effective.

Steel is clean except for grease and oil. It is common to clean using surfactants as known in the art. After using the surfactant, the steel is thoroughly washed with hot water. If any scale or rust is found on the surface, it is removed by conventional pickling, preferably with warm sulfuric acid or hydrochloric acid containing a corrosion inhibitor. After pickling, the metal must be completely washed with water. It is recommended that water washing be performed at least twice to prevent excessive acidic substances from being mixed into the phosphating solution. The first stage is cold water and the second and subsequent stages may be hot or cold water as desired.

After this washing step, the metal is immersed in the phosphating solution of the present invention, kept at 70 to 93 ° C., kept in the solution for 30 seconds to 5 minutes,
A desired film is formed. The optimum coating weight depends on the composition of the metal to be treated, the pretreatment step, and the type of subsequent treatment applied to the phosphatized metal.

In one highly preferred embodiment, a phosphating solution is prepared by mixing a building bath solution and an additive solution in a stainless steel processing tank. In a typical installation, to make 100 gallons of treatment liquid, the tank is filled with 3/4 of water and prepared by adding 12.2 gallons of a bath solution of the composition described below. Next, an additive liquid having the composition described below
Addition of 3.7 gallons completes the preparation of the phosphating mixed solution.

The bath solution of this highly preferred embodiment comprises zinc oxide 8
Consisting of 7.5 parts, 2.3 parts of nickel nitrate aqueous solution containing 13.7% by weight of nickel ions, 211.0 parts of 75% phosphoric acid, 6.0 parts of HAS, and 113 parts of nitric acid of 42% Baume. And The additive liquid is prepared by mixing 261.7 parts of calcium hydroxide and 665.4 parts of nitric acid of 42 ° Baume and dissolving this in water to make a total amount of 1000 parts. (All parts described in this paragraph are by weight.) After performing the above phosphate coating treatment, wash the treated product well with water and rinse off the phosphating solution so that this solution is not carried into the next step. To A suitable lubricant is then applied from the aqueous soap solution. After this, it is ready to perform a high degree of drawing or other forming of this type.

During the operation of this method, some sludge accumulates. This sludge must be removed periodically before reaching a concentration that stains the coating. Since the concentration of the solution changes with the continuation of use, the above-mentioned additive solution should be added to the phosphating solution at appropriate intervals to replenish the consumption of the first component.

[Effects of the Invention] As described above in detail, the phosphate coating solution of the present invention is capable of converting all of the hydroxylamine in the treatment solution into an amount sufficient to form a normal conversion film when cooled. As can be seen from the comparison with the one replaced with (conventional product), there is an excellent effect of reducing the amount of generated sludge by 40% or more, and a sufficiently uniform and dense continuous phosphate film is obtained. Extremely useful.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C23C 22/00-22/86

Claims (3)

(57) [Claims] An aqueous composition for phosphating metal surfaces having a pH in the range of 1 to 3.7, wherein (A) at least 1% by weight of zinc ions, (B) up to 3% by weight of calcium ions, (C) at least 1% by weight of phosphate ions,
(D) at least 0.02% by weight of hydroxylamine,
(E) an accelerator other than hydroxylamine, in an amount effective to act as an accelerator, and (F) a metal surface phosphating treatment characterized by containing nickel and / or copper ions in a maximum of 0.1% by weight. Aqueous composition. 2. The composition according to claim 1, which has a pH in the range of 2.5 to 3.5,
-4% by weight, phosphate ion 1-7.5% by weight, hydroxylamine 0.02-0.4% by weight, and nitrate ion 1-7.5% by weight
The aqueous solution composition according to claim 1, comprising: 3. A method of phosphating a metal by contacting the aqueous solution composition of claim 1 with the metal,
The aqueous solution composition contains 1 to 4% by weight of zinc ions, 0.001 to 0.01% by weight of nickel and / or copper ions, 1 to 7.5% by weight of phosphate ions, 0.02 to 0.4% by weight of hydroxylamine, and 1 to 7.5% by weight of nitrate ions. %.