JPS6360294A - Rust preventing method - Google Patents

Abstract

PURPOSE:To improve the rust preventing performance of a metallic material by bringing the material into contact with a soln. contg. soluble V ions and phosphate ions in the presence of water and oxygen which produce corrosive conditions. CONSTITUTION:A metallic material is brought into contact with a soln. contg. soluble V ions and phosphate ions in the presence of water and oxygen which produce corrosive conditions. The phosphate ions lack the function of an oxidizer and the V ions compensate for the function. The V ions form a redox couple in the soln. under the corrosive conditions, show higher redox potential and fulfill the function of an oxidizer. The phosphate ions form a film of a slightly soluble precipitate under the corrosive conditions and has a deposition function. Very high rust preventing performance is obtd. by the presence of the two kinds of ions.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for preventing rust of metal materials.

(Prior art and its problems) Metals generally corrode in the presence of water, oxygen, and electrolyte ions. This is believed to be due to the formation of local batteries on the metal surface and the progress of electrochemical reactions.

In order to prevent this corrosion of metals, a stable extremely thin film, a so-called passive film, is formed on the metal surface. A typical method is to contact a metal material with chromate ions.

This chromate ion is chromate ion (CrO2”
) and steel (Fe), for example, react to produce stable γ-Pet's on the steel surface, the so-called oxidizer (
Oxid 1zer) function and chromium dioxide (CrtOJ) produced by the reduction of chromate ions adheres to the steel surface, the so-called deposition.
n) There are two functions of function. These two functions form a physical barrier film on the steel surface, which exhibits an extremely excellent rust prevention effect.

However, hexavalent chromium, which has a high rust-preventing ability, is highly toxic, and its use is severely restricted in Japan by various laws and regulations. Therefore, research into non-polluting or low-pollution rust preventive agents is being actively conducted.

For example, phosphate-based substances, particularly zinc phosphate, silica phosphate, condensed aluminum phosphate, etc., have attracted attention, and some of them have been put into practical use. However, a phosphoric acid-based substance is a substance produced by a reaction with a metal material, and has only the above-mentioned deposition function of protecting the metal material, and does not have an oxidizer function of oxidizing the surface of the metal material. Therefore, these have inferior rust prevention ability compared to chromate ions.

(Means for Solving the Problems) The present inventors have discovered that when soluble vanadium ions are used in addition to the above-mentioned phosphate ions, extremely high antirust performance can be obtained.

That is, the present invention provides a rust prevention method characterized by contacting a metal material with an environment containing soluble vanadium ions and phosphate ions under corrosive conditions in the presence of water and oxygen.

This soluble ion of vanadium supplements the oxidizer function lacking in the phosphate ion. This ionic species forms an in-solution redox couple under corrosive conditions in the presence of water and oxygen, exhibits a significant redox potential, and performs the oxidizer function described above.

On the other hand, as described by Moe, phosphate ions form a poorly soluble precipitated film (possibly FePO4) under corrosive conditions and have a deposition function. Therefore, the presence of both of these ionic species is essential to the present invention, and the effects of the present invention will not be achieved if either of the ionic species is absent.

The soluble ions of vanadium used in the present invention are an ion group in which the valence of vanadium atoms is trivalent, tetravalent, and pentavalent, such as v3''', VOH'', vo'', vo'', H
Vo7", HV, 05-1HVO3", VOt
”, H3VzO7-, H, VO4-, HVo
, 2-1vo, '-1VO3-1HV20. '-1V2
07'-1V6O13-1V 40H2'-1HtV+
.

02g'-1HV,. 02e'-1VI00211'
Examples include vanadium ion monomers such as - or polymers thereof. In other words, they are roughly divided into orthovanadate ions and condensed vanadate ions, and as is well known, these two ions usually exist as a mixed system in solutions, especially when the pH is near neutral (in the range of 5 to 9). (near), condensed vanadate ions are mainly present, and monomeric orthovanadate ions are present only in trace amounts. This is because orthovanadate ions condense in solution. Condensed vanadate ions are shown in the chemical formula above, and orthovanadate ions are represented by pyrovanadate ions, metavanadate ions, trivanadate ions, tetravanadate ions, hexavanadate ions, decavanadate ions, etc. It is a condensate of vanadate ions condensed in various proportions. The form of vanadate ion present in the solution is known, and its degree of condensation and pH
It varies depending on the situation. Among these ions, when vanadium is trivalent, in a system where water and oxygen exist, it forms a monovalent and pentavalent redox couple due to the action of oxygen.

On the other hand, phosphate ions include orthophosphate ions, pyrophosphate ions, tripolyphosphate ions, more condensed phosphate ions, trimetaphosphate ions, tetrametaphosphate ions, and ion species generated by the dissociation equilibrium of more condensed metaphosphates. 13i1 body or polymer. The ion form of these phosphate ions in a solution changes depending on the degree of condensation and pH, and they usually exist as a condensate in a solution.

This type of ion supply method may include adsorption onto an ion carrier such as an ion exchange resin or an inorganic ion exchanger (eg, hydrotalcite). Alternatively, a composite oxide of a compound containing a phosphate ion and a compound containing a soluble vanadium ion may be fired at a high or low temperature and used in the form of a powder.

A compound or a carrier containing the above-mentioned ionic species may be blended into antirust wax, paint, lining, etc., and brought into contact with the metal material. Alternatively, an aqueous solution containing the above ionic species may be sprayed onto the surface of the metal material to obtain a temporary rust prevention effect. If the presence of the above ionic species adversely affects the stability of paints or other compositions, compounds or carriers containing the ionic species may be coated with various substances for use.

The metal materials to which the present invention is applied are steel, high strength steel, high tensile steel,
Examples include plated steel sheets, alloys such as stainless steel, cast iron, aluminum and its alloys.

The corrosion conditions under which the present invention is effective are those in which at least water or oxygen is present, and other ions (for example, chloride ions) etc. that are considered to promote corrosion may also be present. The optimum corrosion conditions for the method of the present invention are within the pH range of 5-9. If it exceeds this range, the antirust effect will decrease.

(Effects of the Invention) The rust prevention method of the present invention generates the rust prevention function by both phosphate ions and soluble vanadium ions, and exhibits a rust prevention ability equal to or greater than that of chromate ions. The present invention provides an excellent rust prevention method for metal materials that is pollution-free and low-pollution. Corrosion suppressed by the method of the present invention includes corrosion loss, corrosion cracking, yarn end corrosion, pitting corrosion, end face corrosion, and corrosion of processed parts such as bending.

(Example) The present invention will be explained in more detail with reference to Examples.

Example I and Comparative Example 1 This example shows the difference in orthophosphate ion (po, 3-) and the effect of addition. Various ions (e.g. "CrO*" -1V
043-0.05M), and further PO,"
The corrosion rate of a cold rolled steel plate (JIS G3141) in an aqueous solution with and without addition of - was determined by gravimetric method. The results are shown in Figure 1.

In addition, the corrosion potential of this copper plate in water was measured using a silver-silver chloride electrode (
FIG. 2 shows the results of measurement with a potentiometer using Ag/Agcσ/3.33N KC&) as a reference electrode.

Note that the temperature of the liquid was 20°C.

As is clear from Figure 1, orthophosphate ion (PO
, ") alone, the corrosion rate was reduced by about 1/10 compared to the case without additives (Fig. 1A), and the conventionally known antirust properties of phosphate ions were confirmed in this example as well.

However, the chromate ion (CrO*'- ion) in Figure 1B or the tungstate ion (WO
4! -), no effect of addition of PO43- is observed. In comparison, molybdate ion (M, 0.
2-), when borate ions (BO33-) or silicate ions (SiO3'-) coexist with PO43- ions (Fig. 1 C and F), the coexistence effect is large;
There is no significant difference in the corrosion rate compared to the case of PO,'-ion alone. However, vanadate ion (v
When CrO4''-) and PO43- ions coexist, the corrosion rate is extremely suppressed, resulting in a corrosion rate equal to or lower than that of CrO4''- ions, and exhibits an extremely effective corrosion inhibiting effect.

As is clear from FIG. 2, in the coexistence of PO4", vo, and '- ions, the potential is significantly lower than that of other combinations, indicating good rust prevention ability.

Example ■ and Comparative Example ■ This example demonstrates the coexistence effect of phosphate ions (po, '!-) and soluble vanadium ions (vo, ''''') in the rust prevention of chromate ions (CrO4''-). It is shown by the similarity with the mechanism.

An aqueous solution in which only Cr0h'- ions were added at various concentrations in 3% NaCl2 (air open system with pH = 7), an aqueous solution with various concentrations of PO43- ions and VO43- ions, or WO ,”- and ■043-
(JIS G31)
The corrosion rate and corrosion potential of 41) were measured in the same manner as in Example ①. The results are shown in Figure 3. CrO42- in Figure 3
The addition solution of PO43- and vo is indicated by △ (comparative example).
, '− added solutions are indicated by * (example). As is clear from FIG. 3, since the measurement examples of the comparative example and the example are on one curve, it is considered that the method of the present invention is extremely similar to the rust prevention mechanism of chromate ions. Furthermore, from Fig. 3, the coexistence system of tungstate ions (WO,'') and phosphate ions is clearly different from the rust prevention mechanism of the present invention. For example, when the passive behavior of the same surface is examined by measuring the anodic polarization curve (Fig. 4), it is found that approximately 250 mV is observed on the anodic polarization curve, especially in the region of Fig. 3 where the corrosion rate is smaller than l mdd. It was confirmed that a passive region with a width greater than 10% was developed and showed a curve similar to that of chromate ions.In other words, it is assumed that a stable film is formed on the steel surface. A rolled steel plate (SPCC) was pre-immersed in a solution containing 0.05 mol of chromate ions and a solution containing 0.05 mol of vanadate ions + 0.05 mol of phosphate ions for two weeks. 0.025 mol NatB407+ l 0H20+0
．． 1 mol of NaC (1 OmV/min in a solution of 2,
The potential-current curve at this time was measured. Note that this is an open air system at 25°C. In FIG. 4, X is the polarization curve of a sample that has not been immersed in advance, Y is a polarization curve of a sample that has been immersed in a vanadate ion and phosphate ion coexistence system, and Z is a sample that has been immersed in chromate ion. Furthermore, as judged from the example shown in FIG. 3, the antirust ability of the present invention is exhibited by the coexistence system of vanadium soluble ions and phosphate ions, and the combination of these two types of ions is The concentration of soluble vanadium ions is 0°001 mol and the concentration of phosphate ions is 0.
In a coexisting system with a concentration of 0.01 mol or more, the rust-preventing effect is sufficiently exhibited, and preferably,
Soluble vanadium ion is 0001 to 0.05 mol, phosphate ion is 0.0001 mol to 0.05 mol. O ranges from 1 mol to 0.1 mol, and the concentration ratio (composition ratio) of these two types of ionic species is [V
043-3/[P 0.3-co 5 times to 0. A range of OI times is preferable. These are also the ranges in which the effect of increasing the potential and the effect on the corrosion rate correspond. Under the conditions of this example, the corrosion potential is preferably in the range of -660 mV or more at a corrosion rate of 1 mdd or less.

Next, four types of systems (NaCQ Na5P 04 V2
O5 series, NaCQ Na5PO, V2O3 series, NaC
12-5rCr O4 system and NaC (, Na5P04
The corrosion weight loss due to p II change was determined for (system). The pH of the liquids was adjusted by adding llCa or NaOH to these liquids, and the pH was adjusted to 30°C in an open air system at 25°C.
The corrosion loss of the cold rolled steel sheets immersed in each solution after 1 day was determined by gravimetric method. The results are shown in FIG.

In the NaCQ-Na3P04 system, corrosion loss is large, and NaC
In the Q-8r Cr O4 system, the weight loss is small, a result known from the past. In comparison, NaC
l2-Na5P 04-V2O3 system and NaC(!N
The a5P O4V to 5 system exhibits effective rust prevention ability, and exhibits rust prevention ability equivalent to or greater than that of chromate ions. The antirust ability is especially excellent within the pH range of 5 to 9.

Example ■ and Comparative Example ■ This example examines the rust prevention ability of vanadium soluble ion species before being added to the solution and the phosphate ion species added, using chromate ion as a comparative example. Demonstrate effectiveness.

When various ions are added to 3% Na CQ, the corrosion loss of a cold rolled steel plate at 25°C in an open air system is smaller than that with the addition of chromate ions, marked with ○, and when approximately the same amount is marked with △.
The rust prevention ability is indicated by a mark, and an X mark indicates a larger value. The results are shown in Tables 1 to 2.

Table 1 shows the effect of phosphate ion species, and Table 2 shows the effect of vanadium soluble ion species. The pH of the solution was adjusted to 7.

Table-1 Table-2 Example ■ and comparative example ■ This example shows the effect of oxygen in solution.

Measurement was carried out using the cell shown in FIG. glass container 1
Cold rolled steel plate 2 and pre-deoxidized 0°01% Na
pl with 0.05 mol of phosphate ion and 0.05 mol of vanadate ion coexisting in Cσ (solution 3 of = 7 or only 0.05 mol of phosphate ion in deoxygenated 0.01% NaCQ) The added pH-7 solution 3 is put in a nitrogen gas atmosphere, and various membranes 4 with different oxygen permeation rates are fixed on the top surface of this container 1, and oxygen enters through the gap between the membrane 4 and the top surface of the container 1. In order to prevent this, grease was applied to the top surface of the container L in advance. After performing these operations, the whole was left standing in the air, and the relationship between the corrosion loss of the steel plate 2 and the oxygen permeation rate of the membrane was investigated. The results are shown in Figure 7.

From Figure 7, the coexistence effect of phosphate ions and vanadate ions is such that oxygen
It can be seen that this can be achieved by replenishing more than ee・am Hg).

The oxygen permeation rate of the membrane used here was determined by a commonly used electrochemical method.
This is a sophisticated method.

[Brief explanation of drawings]

FIGS. 1 and 2 are drawings showing the coexistence effect of two types of ionic species in Example (1) and Comparative Example (2). FIG. 3 is a diagram showing the relationship between corrosion potential and corrosion rate in Example ① and Comparative Example H. FIG. 4 is a diagram showing measured polarization curves. FIG. 5 is a diagram showing corrosion loss of a cold rolled steel plate. FIG. 7 is a diagram showing the measuring device used in the sixth men's jar Example (2) and Comparative Example (2), and FIG. 7 is a diagram showing the results. ; 1 In FIG. 6, ■ indicates a container, 2 indicates a cold-rolled plate, 3 indicates a solution with a pH of 7, and 4 indicates a membrane. Agent Patent attorney Aoyama Ao and 2 others Figure 2 (Coexistence > fi) Figure 6 Figure 7 10"10" Iσ141σ121o → 0f
IXf) afif, 'rf1313'4-11 (mf
-cm /cm2゛sea -cm HQ) Procedural amendments Dear Commissioner of the Patent Office, November 1988 2601 Display of the case Patent application No. 204794 of 1988 2, Title of the invention Rust prevention method 3, Person making the amendment Case and Relationship Patent Applicant ■ 2-1-2 Oyodokita, Oyodo-ku, Osaka-shi, Osaka Prefecture Name 1 Nippon Paint Co., Ltd. Representative: Yu Sasaki 4, Agent Address: 2-1, Mihigashi-ku, Osaka-shi, Osaka 540 Prefecture 61
No. 6, Subject of amendment The column of "Detailed explanation of the invention" of the specification and 7. Contents of amendment ■ The following parts in the description are corrected. (1) On page 3, line 15, the phrase ``comprise'' is corrected to ``come to compose, and as a result.'' (2) On page 4, line 6, delete “HV Ot'J.” (3) On page 1, line 7, delete “rHV O3+, J.” (4) On page 71, line 12. In the line, ``In other words, orthovanadate ion'' should be corrected to ``In other words, vanadium ion, vanadyl ion, orthovanadate ion.'' (5) On page 1, line 13, the phrase "generally classified" is corrected to "generally classified, and orthovanadate ions and condensed vanadate ions are particularly preferred." (6) On page 4, line 14, "public knowledge" should be corrected to "well known." (7) Page 5, lines 8-9, “Among these ions,
...by the action of oxygen" [These ions are
"In a system where water and oxygen exist," is corrected to "In a system where water and oxygen exist." (8) Page 5, line 1 O, after ``constituting.'' ``Also, when vanadium is trivalent, soluble ions of tetravalent and pentavalent vanadium are generated by the action of oxygen in an aqueous solution, so redox constitute a couple.” is inserted. (9) On page 6, line 4, the phrase ``complex oxide'' is corrected to ``the mixture may be made into powder, or the mixture thereof.'' (I O) Page 7, line 17, "l"CrO3'-J is corrected to rCrO,'-j. (11) Page 9, line 6, rPCh3-J is changed to "Po
43-j. (12) Insert "Kaishiki Koi Plate and Salt-based Koi Plate" above the first line of page 12. (13) Line 8, γ, line 7 from directly below No. 15, 1″ Correct the phrase “oquinovanadate ion” to “vanadyl ion.” (14) On the 3rd to 2nd lines from the bottom of page 15, the words "ochimvanadate ion" are corrected to "vanadyl ion." (15) In the following places, the word "mole" is corrected to "1 mole/Q". However, if "mole" appears multiple times in one line, all of them should be corrected to "mole/+2J." Il, (+) Figures 2, 3, and 4
Correct the figure as shown in the attached sheet. Above is Figure 2 (coexistence ion concentration O

Claims (1)

[Claims] 1. A rust prevention method characterized by contacting a metal material with an environment containing soluble vanadium ions and phosphate ions under corrosive conditions in the presence of water and oxygen. 2. The rust prevention method according to item 1, wherein the pH of the corrosion condition is 5 to 9.