JP2007162047A - Corrosion preventive inhibitor for aluminum or aluminum alloy material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a corrosion preventive inhibitor for an aluminum or aluminum alloy material with which a corrosion protection film is formed on the surface of the aluminum or aluminum alloy material, and the corrosion of the aluminum or aluminum alloy material can be effectively suppressed, and which is composed of few components and can easily and surely perforn its component management. <P>SOLUTION: This corrosion preventive inhibitor for the aluminum or aluminum alloy material is composed of an aqueous solution of ≥5C organic fluorine compounds. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an anticorrosion inhibitor for aluminum or aluminum alloy materials used for suppressing corrosion caused by liquids used in heat exchangers, radiators, storage tanks and the like made of aluminum or aluminum alloy materials.

  Aluminum alloys have high specific strength and high thermal conductivity, so they are used as materials for heat exchangers such as open rack vaporizers and automobile radiators that vaporize large quantities of liquefied natural gas, or storage tanks for liquefied natural gas carriers. It has been. In these devices, a corrosion inhibitor (anticorrosive inhibitor) is often added and used in order to prevent corrosion of the constituent material by a refrigerant or the like.

  For example, a corrosion inhibitor of magnesium and aluminum is used as a coolant for an automobile engine. As such a corrosion inhibitor, in Patent Document 1, a) one or more kinds selected from the group consisting of a) an alkylbenzoic acid, a C5-C15 monobasic acid and a C5-C15 dibasic acid or a salt thereof. Corrosion inhibitor formulations are disclosed that contain 0.1 to 15% by weight inhibitor and b) 0.005 to 5% by weight fluoride and / or fluorocarboxylic acid or salt thereof. Also, fluorine compounds such as fluorides and / or fluorocarboxylates, when used alone, provide a very low degree of protection, but in combination with aliphatic carboxylates or alkylbenzoic acids, especially at high temperatures. It has been disclosed to provide a synergistic effect that significantly prevents magnesium corrosion.

  On the other hand, in Patent Document 2, the fluoride disclosed in Patent Document 1 has a high anticorrosion property against magnesium, but has an adverse effect on the aluminum alloy. A cooling liquid composition having a melting point depressant selected from glycols and alcohols as a main component, and a corrosion inhibitor selected from fluoride, and a tribasic acid of organic carboxylic acid or its A coolant composition containing an alkali metal salt is disclosed.

  On the other hand, Patent Document 3 discloses sodium alkyl diaminoethyl glycine, alkyl diaminoethyl glycine hydrochloride, alkyl hydrochloride to prevent corrosion of the storage tank during a hydraulic test of an aluminum alloy storage tank of a liquefied gas or liquefied natural gas carrier. An anticorrosive agent for an aluminum or aluminum alloy tank comprising an aqueous solution obtained by mixing one or more compounds selected from the group consisting of a formalin condensate of polyaminoethylglycine and dicyandiamide is disclosed.

Special Table 2002-527619 JP 2005-325300 A JP-A-6-336684

  However, there is a need for anticorrosion inhibitors for aluminum or aluminum alloy materials with even higher performance. Further, as shown above, conventional anticorrosive inhibitors generally have a problem that component management is not easy because they are multicomponent systems. In addition, fluorine compounds are effective components as corrosion inhibitors for aluminum or aluminum alloy materials, but conventional fluorine compounds used as corrosion inhibitors for aluminum or aluminum alloy materials generally tend to be fluorine ions in solution. There is a problem that there is a limit as a corrosion inhibiting effect due to inorganic acids and inorganic salts such as hydrofluoric acid, sodium fluoride, potassium fluoride and ammonium fluoride.

  In view of such conventional problems, the present invention provides an aluminum or aluminum alloy material that can effectively prevent corrosion of aluminum or aluminum alloy material by forming an anticorrosive film on the surface of aluminum or aluminum alloy material. An object is to provide an inhibitor for corrosion protection. It is another object of the present invention to provide an anticorrosion inhibitor for aluminum or aluminum alloy material which can be easily and reliably managed with a small amount of components.

  The inhibitor for corrosion protection of aluminum or aluminum alloy material according to the present invention comprises an aqueous solution of an organic fluorine compound having 5 or more carbon atoms.

  In the above invention, the organic fluorine compound having 5 or more carbon atoms preferably has a COOH, COF or COCl end group. The aqueous solution is preferably one in which 50 to 500 ppm of an organic fluorine compound is dissolved, and further one in which manganese or nickel chloride is dissolved. In this case, manganese or nickel chloride is preferably contained in an amount of 20 to 50 ppm in terms of ions.

  Since the inhibitor for corrosion protection of aluminum or aluminum alloy material according to the present invention has a high corrosion inhibiting effect and is composed of a small number of components, the component management can be easily performed.

  Embodiments of the anticorrosion inhibitor for aluminum or aluminum alloy material according to the present invention will be described below. The inhibitor for corrosion protection of aluminum or aluminum alloy material according to the present invention comprises an aqueous solution of an organic fluorine compound having 5 or more carbon atoms. That is, it consists of an aqueous solution of an organic fluorine compound, not a fluorine compound of an inorganic acid or inorganic salt.

  The organic fluorine compound used in the present invention is an organic fluorine compound having 5 or more carbon atoms. Thereby, a high corrosion inhibitory effect can be obtained for aluminum or aluminum alloy material. Such a corrosion inhibiting effect of the organic fluorine compound is exhibited by forming a film on the surface of the aluminum or aluminum alloy material, as will be described later. Therefore, from the viewpoint of film forming ability, the organic fluorine compound is preferably an aliphatic hydrocarbon organic fluorine compound in which straight-chain molecules are likely to be arranged almost vertically on the surface of the aluminum or aluminum alloy material. That is, the organic fluorine compound used in the present invention is preferably an aliphatic hydrocarbon organic fluorine compound having polarity. In addition, the organic fluorine compound preferably has a COOH, COF, or COCl end group.

  In the present invention, such an organic fluorine compound dissolved in an aqueous solvent is used. That is, the inhibitor for corrosion protection of aluminum or aluminum alloy material according to the present invention has a configuration in which a predetermined organic fluorine compound is simply dissolved in pure water, so that component management can be easily performed. In general, an organic fluorine compound has a characteristic that it becomes difficult to dissolve in water as its carbon number increases. For this reason, the organic fluorine compound used in the present invention is determined by the corrosion inhibitory effect exerted and the solubility in pure water, and those having a carbon number of 30 or less and 1000 or less in terms of molecular weight are used.

  In FIG. 1, the corrosion inhibitory effect test result of the inhibitor for corrosion prevention of the aluminum or aluminum alloy material which concerns on this invention is shown. Fig. 1 shows the weight loss of an aluminum alloy specimen when the 3% NaCl solution is adjusted to pH 1 with hydrochloric acid and 1000 ppm of various organic fluorine compounds are dissolved and the aluminum alloy specimen is kept at 30 ° C for 48 hours. It is a graph. In FIG. 1, the horizontal axis represents a corrosive solution containing various organic fluorine compounds, and the vertical axis represents mass loss. The symbol COOH, COF, or COCl shown on the horizontal axis in FIG. 1 represents the end group of the organic fluorine compound in the corrosive liquid. Symbols C2 to C15 indicate the number of carbon atoms of the organic fluorine compound, specifically, the organic fluorine compounds shown in Table 1. CNT indicates the case of a corrosive solution in which a 3% NaCl solution not containing an organic fluorine compound is adjusted to pH 1 with hydrochloric acid.

  In addition, the said test was done with the test apparatus shown in FIG. That is, a test piece 15 (A3003, 9 × 9 mm) made of an aluminum alloy material was immersed in a container 13 filled with the above-described corrosive liquid 10 containing an organic fluorine compound, and a corrosion inhibitory effect test was performed. The corrosive liquid 10 was sent to maintain a constant temperature by the thermostatic bath 100 provided with the temperature controller 120 and to keep the dissolved oxygen concentration of the corrosive liquid 10 constant by the air pump 110.

  According to FIG. 1, in the case of an organic fluorine compound having a COOH end group, it can be seen that the weight loss tends to decrease as the number of carbons increases. In the case of an organic fluorine compound having 2 or 4 carbon atoms (C2, C4), the weight loss is slightly less than in the case of CNT, but in the case of an organic fluorine compound having 5 or 7 carbon atoms (C5, C7) Is less than half that of CNT. In particular, in the case of an organic fluorine compound having 8 carbon atoms (C8), the weight loss is 1/100 that of CNT. In addition, when C5 and C8 specimens (with 5 and 8 carbon atoms) were observed after the test, a white film was observed on the surface in the case of C5 specimens, and a metallic luster was exhibited in the case of C8 specimens. The presence of a thin dense film was confirmed by QCM measurement (quartz crystal microbalance measurements). That is, the inhibition of corrosion is caused by the formation of an organic fluorine compound film on the aluminum alloy surface. In addition, QCM measurement was performed using Seiko EG & G Co., Ltd. QCA922.

  The case of the organic fluorine compound having a COF end group also has the same tendency as the case of the organic fluorine compound having a COOH end group, and the weight loss decreases as the number of carbon atoms increases. In addition, according to FIG. 1, the organic fluorine compound having a COOH end group having 5 or more carbon atoms, the organic fluorine compound having a COF end group, and the organic fluorine compound having a COCl end group have a weight loss of 1 / It turns out that it is 2 or less.

  Fig. 3 shows the relationship between the concentration of C8 organofluorine compound dissolved in the corrosive solution under the same conditions as in Fig. 1 and the weight loss of aluminum alloy in the case of organofluorine compound (C8) having COOH end groups. It is a graph which shows the result of having investigated. In FIG. 3, the horizontal axis represents the concentration of the organic fluorine compound (C8) having a COF end group, and the vertical axis represents the weight loss of the aluminum alloy. According to Fig. 3, in the concentration range of organic fluorine compounds from 0 to 40 to 60 ppm, the weight loss decreases rapidly with increasing concentration, then the weight loss decreases, and when the concentration exceeds 100 ppm, the weight loss is very high. It turns out that it becomes small and becomes saturated. That is, in the case of the organic fluorine compound (C8) having a COOH end group, it can be seen that a sufficient corrosion inhibiting effect can be obtained with an aqueous solution having a concentration of 50 to 500 ppm, and the concentration may be about 50 to 150 ppm. .

  Thus, corrosion of the aluminum alloy can be effectively suppressed by an aqueous solution in which a trace amount of one type of organic fluorine compound is dissolved. This corrosion inhibiting effect can be obtained in the same manner even with aluminum. Further, the aqueous solution of the organic fluorine compound only needs to be an aqueous solution having a predetermined organic fluorine compound concentration in the state of use, and the supply form of the anticorrosive inhibitor of the aluminum or aluminum alloy material according to the present invention is a tablet form. May also be in the form of a stock solution.

  Moreover, the inhibitor for corrosion protection of the aluminum or aluminum alloy material according to the present invention is not limited to the above-described embodiment. A small amount of one type of organic fluorine compound may contain other components. For example, the organic fluorine compound may contain a trace amount of metal salt.

Fig. 4 shows a corrosive solution in which 50 ppm of C8 organic fluorine compound is dissolved and aluminum, manganese or nickel chloride (AlCl ₃ · 6H ₂ O, MnCl ₂ · 4H ₂ O or NiCl ₂ · 6H ₂ O) is dissolved It is a graph which shows the mass loss of the test piece which consists of aluminum alloy materials at the time of performing the test similar to FIG. When the metal salt was dissolved, the ion concentrations of Al ³⁺ , Mn ²⁺ and Ni ²⁺ were 29 ppm, 24 ppm and 29 ppm, respectively. In FIG. 4, the numbers on the horizontal axis indicate the corrosive solution in which the C8 organic fluorine compound and AlCl ₃ · 6H ₂ O, MnCl ₂ · 4H ₂ O or NiCl ₂ · 6H ₂ O are dissolved, respectively, and the vertical axis indicates the mass. Indicates weight loss. CNT indicates the case of a corrosive solution in which only C8 organic fluorine compound is dissolved.

According to FIG. 4, it can be seen that the presence of Mn ²⁺ and Ni ²⁺ in the aqueous solution of the organic fluorine compound increases the corrosion inhibition effect. This indicates that there may be a cooperative action between the organofluorine compound and the metal ion, as will be explained below. In this example, the effect is obtained in the case of the C8 organofluorine compound and the Ni ²⁺ ion. It shows the highest. This cooperative action is exhibited if manganese or nickel chloride is contained in an amount of 20 to 50 ppm in terms of ions.

FIG. 5 is a graph showing the weight loss of an aluminum alloy when a test is performed using a corrosive solution in which only a metal salt not containing an organic fluorine compound is dissolved. According to FIG. 5, the corrosion inhibition effect is opposite to that in FIG. 4, and the corrosion inhibition effect is higher in the order of Ni ²⁺ , Mn ²⁺ , and Al ³⁺ , with Ni ²⁺ ions being the most corrosion inhibition. It turns out that the effect is small. That is, the result of FIG. 4 is a result of enhancing the corrosion inhibition effect by the cooperative action of the C8 organofluorine compound and Ni ²⁺ ions. The test conditions in the case of FIG. 5 are the same as in FIG. The metal salts used and their metal ion concentrations in the corrosive liquid are the same as in FIG.

It is a graph which shows the corrosion inhibitory effect test result with respect to the aluminum alloy test piece of the inhibitor for corrosion prevention of the aluminum or aluminum alloy material which concerns on this invention. It is a schematic diagram of the test apparatus used for the test of FIG. It is a graph which shows the relationship between the density | concentration of an organic fluorine compound, and the mass loss with respect to an aluminum alloy test piece. It is a graph which shows the mass loss of the aluminum alloy test piece by the corrosive liquid containing an organic fluorine compound and a metal salt. It is a graph which shows the mass loss of the aluminum alloy test piece by the corrosive liquid containing only a metal salt.

Explanation of symbols

10 Corrosive liquid
13 containers
15 specimens
100 temperature chamber
110 Air pump
120 Temperature controller

Claims (5)

  An anticorrosion inhibitor for aluminum or aluminum alloy material comprising an aqueous solution of an organic fluorine compound having 5 or more carbon atoms.   The inhibitor for corrosion protection of aluminum or aluminum alloy material according to claim 1, wherein the organic fluorine compound having 5 or more carbon atoms has a COOH, COF or COCl end group.   The inhibitor for corrosion protection of aluminum or aluminum alloy material according to claim 1 or 2, wherein the aqueous solution is obtained by dissolving 50 to 500 ppm of an organic fluorine compound.   The inhibitor for corrosion protection of aluminum or aluminum alloy material according to any one of claims 1 to 3, wherein the aqueous solution is obtained by further dissolving manganese or nickel chloride.   The inhibitor for corrosion protection of aluminum or aluminum alloy material according to claim 4, wherein manganese or nickel chloride is contained in an amount of 20 to 50 ppm in terms of ions.

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