An inorganic anticorrosive coating with dual functions of chloride ion fixation and damage self-repair

Abstract

The application discloses an inorganic anticorrosive coating with functions of fixing chloride ions and self-repairing damages, characterized in that the coating comprises the following components by weight: 30-70 parts of a matrix phase, 10-40 parts of a hydroxyapatite phase, 10-30 parts of a phosphate phase and 10-20 parts of a fluxing phase; part of the phosphate phase can interact with the matrix phase to jointly form a basic film-forming substance, and form an unreleasable phosphate phase which is not easy to dissolve out during service of the coating; part of the phosphate phase is distributed in the basic film-forming substance through a filling effect, and is dissolved out under specific induced conditions to form a releasable phosphate phase. The coating is a pure inorganic material and has good durability; the hardness reaches 300-1000 HV; the coating remains stable in the concrete without chloride ion pollution; when the chloride ions reach the surface of the coating, the coating can fix the chloride ions to reduce the corrosion of the steel bars; in the case that the coating is damaged and the chloride ion corrosion exists, a protective precipitate film is formed in the damaged area, and the effect of self-repairing damages is achieved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of corrosion protection of reinforced concrete structure, and particularly relates to an inorganic anticorrosive coating with the dual functions of chloride ion fixation and damage self-repairing for reinforcing bar corrosion protection. BACKGROUND

[0002] The construction of marine islands and reefs is of great significance to the improvement of the far-sea combat capability of the navy, and the long-term safe service of military infrastructure on the islands is the backup foundation guarantee for the life of the military personnel and the safety of the equipment. At present, the construction of military wharfs and island infrastructure is mainly based on concrete structures. However, the corrosion of chloride ions in the marine environment and the carbonation of concrete can cause the corrosion of reinforcing bars in the concrete structure, resulting in the destruction of the concrete structure and seriously affecting the service life and safety of the military infrastructure.

[0003] Reinforcing bar anticorrosive coating can effectively improve the corrosion resistance of reinforcing bars. Generally, a good coating has good anticorrosive effect, but defects and damages will inevitably occur in the coating during construction and service, providing a penetration path for corrosive media and thus seriously reducing the anticorrosive performance of the coating. Damage self-repairing coating can release solidifying agents or corrosion inhibitors when the coating is damaged, and thus physically repair the coating or form a protective film, thereby reducing the corrosion of reinforcing bars. However, most of the damage self-repairing coatings are organic materials, which have the disadvantages of poor aging resistance, etc. In addition, the low hardness of organic coatings will increase the bonding slip between reinforcing bars and concrete and reduce the bonding strength. Although inorganic coatings have advantages in material durability, mechanical strength, heat resistance, etc., they generally do not have the ability of damage self-repairing. Therefore, how to develop an inorganic anticorrosive coating with high durability, high mechanical strength and damage self-repairing has become a problem to be solved for the development of long-life concrete structures. SUMMARY

[0004] In order to overcome the shortcomings of the prior art, the present application provides an inorganic anticorrosive coating with high durability, high hardness, and the dual functions of chloride ion fixation and damage self-repairing.

[0005] The technical problem solved by the present application is solved by the following solution: an inorganic anticorrosive coating with the dual functions of chloride ion fixation and damage self-repairing, comprising the following components by weight: 30-70 parts of a matrix phase, 10-40 parts of a hydroxyapatite phase, 10-30 parts of a phosphate phase, and 10-20 parts of a fluxing phase; part of the phosphate phase can interact with the matrix phase to form a basic film-forming material, and form a non-releasable phosphate phase which is not easy to dissolve out during the service of the coating; another part of the phosphate phase is distributed in the basic film-forming material by filling, and dissolves out under specific induced conditions to form a releasable phosphate phase.

[0006] Further, the matrix phase is composed of three parts, the first part is any one or combination of two of sodium borate and potassium borate, the second part is any one or combination of two of sodium carbonate and potassium carbonate, and the third part is sodium silicate and calcium fluoride.

[0007] Further, the hydroxylapatite phase is any one or combination of two or more of hydroxyl calcium apatite, hydroxyl magnesium apatite, hydroxyl sodium apatite, hydroxyl potassium apatite and derivatives thereof.

[0008] The hydroxylapatite phase, the hydroxylapatite raw material is screened through a 200-mesh sieve, the hydroxylapatite has sufficient stability, compatibility and chemical inertness in the matrix phase, can be uniformly distributed in the coating and form a network structure, and is closely combined with the matrix.

[0009] Further, the phosphate phase is any one or combination of two or more of sodium phosphate, potassium phosphate, zinc phosphate and magnesium phosphate.

[0010] Further, the fluxing phase is any one or combination of two or more of boron oxide, diaphosphorus pentoxide, bismuth oxide and zinc oxide.

[0011] Further, the thickness of the coating is 50-500 μm.

[0012] Further, the coating is applied to the surface of the steel bar at a high temperature of 400-700 °C.

[0013] An inorganic anticorrosive coating with the functions of fixing chloride ions and self-repairing damages as described above, the coating is composed of pure inorganic materials, and has no any change after xenon lamp aging test for 8000 h, and has excellent self-durability. The hardness of the coating is high, and the Vickers hardness can reach 300-1000 HV, which is beneficial to the adhesion between the coated steel bar and the concrete, and especially can improve the adhesion stiffness in the small slip stage.

[0014] An inorganic anticorrosive coating with the functions of fixing chloride ions and self-repairing damages as described above, the coating has the function of fixing chloride ions. In the initial stage of the construction of concrete structure, the pore solution of the concrete is mainly saturated calcium hydroxide, and the pH is about 12-13.5, at this time, the coating can remain relatively stable in the pore solution of the concrete; as the chloride ions completely penetrate the concrete and reach the surface of the coating, the coating plays a physical barrier role to isolate the corrosion medium and the steel bar substrate, and on the other hand, under the conditions of the alkaline pore solution of the concrete and the chloride ions, the uniformly and network-distributed hydroxylapatite phase in the coating is activated, and reacts with the chloride ions to generate chlorapatite, thereby fixing the chloride ions and consuming the corrosive chloride ions, and effectively inhibiting the occurrence of steel bar corrosion.

[0015] An inorganic anticorrosive coating with the dual functions of fixing chloride ions and damage self-repairing as described above, the coating has the function of forming a protective film for damage self-repairing. If the coating on the surface of the steel bar in the concrete is damaged, the chloride ions will cause slight corrosion of the exposed part of the steel. At this time, the anode generates an oxidation reaction of iron to generate iron ions, and the cathode generates a reduction reaction of oxygen to generate hydroxyl ions. The change of the local microenvironment (ion concentration, pH value, etc.) promotes the dissolution of the phosphate in the releasable phosphate phase in the coating. As a crystal nucleus, chlorapatite promotes the crystallization and growth of the released phosphate and free calcium ions in the pore solution of the concrete, forming a protective precipitate film on the surface of the exposed steel bar, hindering the further development of corrosion.

[0016] In summary, the present application has the following advantages and outstanding technical effects: (1) it is a pure inorganic material, and there is no change after xenon lamp aging test for 8000h, and the coating itself has excellent durability; (2) the hardness of the coating is high, reaching 300-1000HV, which is beneficial to reduce the bonding slip between the steel bar and the concrete; (3) the coating remains stable in the concrete without chloride ion pollution, and when the chloride ions reach the surface of the coating, the coating can fix the chloride ions to reduce the corrosion of the steel bar; (4) in the case of coating damage and chloride ion corrosion, a protective precipitate film will be formed in the damaged area, achieving the effect of damage self-repairing; (5) the application range is wide, and it is suitable for steel bar corrosion prevention in concrete structures, and also suitable for corrosion prevention of steel or other metals in other alkaline and chloride ion corrosion environments. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 Pictures of the present application examples 1-3 after xenon lamp aging test for 8000h.

[0018] Figure 2 EDS spectrum of chlorapatite on the surface of the present application example 1.

[0019] Figure 3 Development and change of the surface of the present application example 2 when immersed in the pore solution of the concrete. DETAILED DESCRIPTION

[0020] In order to enable the personnel in the technical field to better understand the present application scheme, the technical solutions in the inventive examples will be described below, and obviously, the described examples are only a part of the examples of the present application, but not all the examples. Based on the examples in the present application, all other examples obtained by the ordinary skilled in the art without making creative efforts should belong to the protection scope of the present application.

[0021] Example 1

[0022] An inorganic anticorrosive coating with the dual functions of fixing chloride ions and self-repairing damages, comprising the following components by weight: 50 grams of sodium borate, 25 grams of potassium borate, 50 grams of sodium carbonate, 50 grams of sodium silicate, 25 grams of calcium fluoride, 125 grams of hydroxyapatite, 50 grams of sodium phosphate, 25 grams of potassium phosphate, 50 grams of zinc phosphate, 25 grams of boric oxide, and 25 grams of bismuth oxide. The coating is applied to the surface of a steel bar at a high temperature of 680°C, and the thickness of the coating is 225 μm.

[0023] Example 2

[0024] An inorganic anticorrosive coating with the dual functions of fixing chloride ions and self-repairing damages, comprising the following components by weight: 25 grams of sodium borate, 75 grams of potassium carbonate, 40 grams of sodium silicate, 10 grams of calcium fluoride, 100 grams of hydroxyapatite, 100 grams of hydroxyapatite, 75 grams of magnesium phosphate, 25 grams of boric oxide, 25 grams of phosphorus pentoxide, and 25 grams of bismuth oxide. The coating is applied to the surface of a steel bar at a high temperature of 550°C, and the thickness of the coating is 60 μm.

[0025] Example 3

[0026] An inorganic anticorrosive coating with the dual functions of fixing chloride ions and self-repairing damages, comprising the following components by weight: 25 grams of potassium borate, 100 grams of sodium carbonate, 75 grams of potassium carbonate, 100 grams of sodium silicate, 25 grams of calcium fluoride, 25 grams of hydroxyapatite, 25 grams of hydroxyapatite, 25 grams of sodium phosphate, 25 grams of zinc phosphate, 35 grams of phosphorus pentoxide, and 40 grams of zinc oxide. The coating is applied to the surface of a steel bar at a high temperature of 410°C, and the thickness of the coating is 475 μm.

[0027] In order to verify the implementation effect of the present application, the following tests were conducted.

[0028] (1) Coating hardness

[0029] The hardness of the coating was tested by using a microhardness tester equipped with a Vickers indenter. The load dwell time was 10 s, and the indentation load was 0.98 N. The calculation method of the microhardness was as follows:

[0030]

[0031] wherein HV is the Vickers hardness, the unit is MPa; F is the indentation load, the unit is N; S is the indentation projected area, the unit is mm 2 ; and a is the included angle between the faces of the indenter (the Vickers indenter is 136°); d is the average length of the diagonal of the indentation, the unit is mm.

[0032] Through calculation, the hardness of the coating described in Example 1, Example 2 and Example 3 was 975 HV, 620 HV and 330 HV, respectively.

[0033] (2) Xenon lamp aging test

[0034] The surface morphology of the coated rebar was observed after xenon lamp aging for 8000 h using a xenon lamp artificial weathering test device. The results of Examples 1-3 are shown in Figure 1 It can be seen that the surfaces of Examples 1-3 did not change after 8000 h of xenon lamp aging, indicating that the coating described in the present application has excellent self-durability, which is mainly because the coating material described in the present application is all pure inorganic aging-resistant material.

[0035] (3) Fixed chloride ion performance

[0036] The coated rebar of Examples 1-3 was immersed in a mixed solution of saturated calcium hydroxide and 5wt% sodium chloride with a pH of 12.7 to simulate the pore solution of concrete. After 30 days of immersion, the surface of the coating was analyzed by energy spectrum, and the concentration of chloride ions in the solution was tested. Chlorapatite phase was detected on the surface of Examples 1-3 by energy spectrum, and representative results are shown in Figure 2 In addition, ion analysis showed that the concentration of chloride ions in the solution of Example 1, Example 2 and Example 3 was reduced to 17%, 8% and 21% of the original, respectively. This shows that under the conditions of alkaline pore solution and chloride ions of concrete, the hydroxyapatite phase in the coating is activated, which reacts with chloride ions to form chlorapatite, which has the effect of fixing chloride ions, and consumes corrosive chloride ions, thereby effectively reducing the corrosion of the rebar.

[0037] (4) Damage self-repairing performance

[0038] The partially damaged coated rebar of Examples 1-3 was immersed in saturated calcium hydroxide with a pH of 12.7 for 40 days, and then 5wt% of sodium chloride was added to prepare a simulated concrete pore mixed solution, and the morphology change of the coating defect was observed by optical microscope. In a single saturated calcium hydroxide solution, the damage of the coating of Examples 1-3 did not change significantly; after adding sodium chloride, the damaged coating of Examples 1-3 all appeared a protective damage self-repairing film, and representative results are shown in Figure 3 The above results show that in the presence of chloride ions in the pore solution of concrete, the change of the local microenvironment (ion concentration, pH value, etc.) will promote the dissolution of phosphate in the releasable phosphate phase in the coating. At this time, chlorapatite is used as a crystallization nucleus to promote the crystallization and growth of phosphate and calcium ions in the pore solution of concrete, forming a protective precipitate film on the surface of the exposed rebar, which hinders the further development of corrosion.

Claims

1. An inorganic anticorrosion coating with dual functions of chloride ion fixation and damage self-repairing, comprising the following components by weight: a matrix phase 30-70 parts, a hydroxyapatite phase 10-40 parts, a phosphate phase 10-30 parts, a fluxing phase 10-20 parts; part of the phosphate phase can interact with the matrix phase to form a basic film-forming material, and form a non-releasable phosphate phase which is not easy to dissolve out during the service of the coating; another part of the phosphate phase is distributed in the basic film-forming material by filling effect, and dissolves out under inducing conditions to form a releasable phosphate phase; the matrix phase is composed of three parts, the first part is any one or a combination of two of sodium borate and potassium borate, the second part is any one or a combination of two of sodium carbonate and potassium carbonate, and the third part is sodium silicate and calcium fluoride; the phosphate phase is any one or a combination of two or more of sodium phosphate, potassium phosphate, zinc phosphate and magnesium phosphate.

2. The inorganic anticorrosive coating having bifunction of chloride ion fixation and damage self-repairing according to claim 1, characterized in that: The hydroxyapatite phase is any one or a combination of two or more of hydroxy calcium phosphate, hydroxy magnesium phosphate, hydroxy sodium phosphate, hydroxy potassium phosphate and derivatives thereof.

3. The inorganic anticorrosive coating having bifunction of chloride ion fixation and damage self-repairing according to claim 1, characterized in that: The fluxing phase is any one or a combination of two or more of boron oxide, phosphorus pentoxide, bismuth oxide and zinc oxide.

4. The inorganic anticorrosive coating having bifunctions of chloride ion fixation and damage self-repairing according to claim 1, characterized in that: The coating is formed by coating the surface of the steel bar at a high temperature of 400-700 ℃, and has a thickness of 50-500 μm and a hardness of 300-1000 HV.

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