JPS5857511B2 - Phosphate chemical treatment liquid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a phosphate chemical treatment solution with little sludge that forms a crystalline phosphate film on the surface of an iron-based material.

This is a widely used technology in which a phosphate film is applied to the surface of iron-based materials for the purpose of improving corrosion resistance, paint base properties, plastic workability, etc.

Generally, the phosphate chemical treatment method for iron-based materials uses zinc phosphate as the main component, and Mn'', Ni'', and C as necessary.
Iron-based materials are treated with an aqueous phosphate chemical treatment solution containing u2+ and oxidizing agents such as NO, C1O, and NO to form an insoluble crystalline phosphate film.

When iron-based materials are subjected to phosphate chemical conversion treatment by dipping or spraying, first Fe+2HPO−”Fe(HPO)+Hi
As a result of this reaction, iron from the iron-based material is eluted into the phosphate chemical treatment solution while generating hydrogen.

At the interface between the iron-based material and the phosphate chemical treatment solution, the pH is high, and secondary and tertiary phosphates gradually precipitate on the surface of the iron-based material to form a film.

The first solubility caused by the elution of iron from the surface of iron-based materials.
Iron phosphate Fe (H2PO4)2 Ha, ClO3-1
It is oxidized by an oxidizing agent such as NO-, precipitates as insoluble ferric phosphate FePO, and accumulates as sludge.

If this sludge adheres to the heating tube, it will cause a decrease in the heat exchange rate.

Furthermore, if this sludge adheres to the object to be treated, it may cause various troubles in subsequent steps.

The sludge in this bath accumulates at the bottom of the treatment tank over time, but it must be removed periodically or continuously. The less the better.

An object of the present invention is to provide a phosphate chemical treatment solution for iron-based materials that reduces the amount of sludge produced in the phosphate chemical treatment solution compared to conventional methods.

In order to achieve the object of the present invention, the present inventor conducted various studies and found that Z n/P O in the phosphate chemical treatment solution for iron-based materials.
When iron-based materials are subjected to phosphate chemical conversion treatment by maintaining the weight ratio and NO/PO weight ratio within respective ranges and adding an appropriate amount of perchlorate to the chemical conversion treatment liquid, the The amount of sludge generated from the chemical conversion treatment liquid is smaller than that of conventional phosphate chemical conversion treatment liquids, and it has the effect of forming a phosphate film containing a large amount of iron on the surface of iron-based materials. This is what I found.

The phosphate chemical treatment solution of the present invention contains Zn2″-, po3
゜ Contains NO3 and ClO2 as main components, and the Zn/PO weight ratio in the treatment liquid is 0.2 to 1 = 0 and NO3
/PO4 weight ratio is in the range of O03 to 3.0, and further, as CtO-, 0.005 to 201/l, preferably,
0.05~5? It is a zinc phosphate-based chemical conversion treatment solution containing /.

Perchlorates include alkali metal salts such as Na, Mg, and C.
One or more of alkaline earth metal salts such as Zn, Mn, Ni, etc. can be used.

The treatment liquid of the present invention further contains an oxidizing agent selected from No-1Ct〇, and optionally Ca2+.

Cations selected from Mn2+, Ni2+, Cu2+, etc., anions selected from F-1Si0, etc. can be included as a source.

Is the amount of CtO- in the treatment solution of the present invention 0.005 L? If / is less than 20 f/, the effect of the present invention will be small, and even if it is contained more than 20 f/, no improvement in the effect will be obtained.

Perchlorate may be added directly to the phosphate treatment solution;
Also, it may be added to the bath preparation agent, replenisher, etc. of this treatment liquid,
The processing solution may be supplemented with a mixture of an oxidizing agent (for example, NaNQ).

Zn/PO weight ratio is 0.2 or less and 1. The amount of sludge increases in any case of Q or more.

Next, if the NO3/PO4 weight ratio is less than 0.3, the chemical formation properties of the phosphate film formed on the surface of the iron-based material will deteriorate;
．． When it is 0 or more, the amount of sludge increases.

Next, an important point in the present invention is that perchlorate and other oxidizing agents are used together in the treatment liquid of the present invention.

When iron-based materials are treated with a phosphate chemical treatment solution containing only perchlorate as an oxidizing agent, it is not suitable for practical use because the phosphate film formation property is poor, but the treatment solution Fe(HPO) is eluted into Fe(HPO), which forms a larger amount of fine zinc iron phosphate crystals (FeZn2(P
o4) 2・4H20, phosphophyllite
) may cause precipitation.

That is, since the eluted Fe2+ largely contributes as a film component, the oxidation of Fe2+, that is, the formation of sludge due to Fe2+-PFe3+, is reduced.

The sludge produced by gold phosphate chemical conversion treatment of iron-based materials is
Initially, it occurs near the interface between the object to be treated and the treatment liquid and becomes cloudy, but as it diffuses into the bath, it becomes a pale yellow floc and gradually accumulates on the bottom of the bath.

When sampling the sludge deposited at the bottom of the bath and examining the diffraction X-rays using an X-ray diffractometer, a diffraction X-ray image does not appear when the sludge is formed or in the floc-like stage, but as the accumulated sludge ages, a diffraction X-ray image appears. begins to appear.

This is called sludge crystallization, and the sludge volume after crystallization of the phosphate chemical treatment solution of the present invention is 1/2 of that before crystallization.
The amount will be ~1/10.

Next, examples of the present invention will be described.

Example 1 Carbon steel (5TPG 38) was degreased, washed with sulfuric acid to clean the surface, and immersed in an aqueous phosphate treatment solution shown in Table 1 for 10 minutes.

The processing load rate of the processing liquid on the workpiece is 0.03 d/l
So, the processing amount is 2tr? / went.

As Comparative Example 1, M was obtained from the phosphate chemical treatment aqueous solution in Table 1.
The same method was used except for g(CtO).

The test results are shown in Table 2.

*Sample 10rIll, indicator phenolphthalene,
Titrant N/10 NaOH ※※Sample 10-1 Indicator bromophenol blue,
Titrant N/10MaOH Example 2 After degreasing alloy steel (SCM435), the surface was cleaned with sulfuric acid and immersed in the phosphate chemical treatment aqueous solution shown in Table 3 for 10 minutes.

Processing of the object to be processed * Processing load rate of bitter liquor is 0.03r
On December 4th, the processing amount was 2d/1.

As Comparative Example 2, N was extracted from the phosphate chemical treatment aqueous solution in Table 3.
a (Except JO, otherwise the same method was used.

The test results are shown in Table 4. Example 3 A hard steel wire (5WRH32) was degreased, washed with sulfuric acid to clean the surface, and immersed in a phosphate chemical treatment aqueous solution shown in Table 5 for 10 minutes.

The processing load rate of the processing liquid to the workpiece is 0.03r11
/l, the throughput was low.

As Comparative Example 3, M was obtained from the phosphate chemical treatment aqueous solution in Table 5.
The same method was used except for g(Cto).

The test results are shown in Table 6. As described above, the phosphorylating acid treatment liquid of the present invention can reduce the amount of sludge produced compared to the conventional phosphorylation acid treatment liquid.

Claims (1)

[Claims] 1. The Zn/P04 weight ratio and NO3/PO4 weight ratio in the phosphate chemical treatment solution for iron-based materials are each 0.2 to 1.
(and 0.3 to 3°O, and the content of perchlorate in the treatment liquid is 09005 to 201μ as CIO.