A stabilizing treatment agent for promoting the formation of a dense stable rust layer on weathering-resistant steel

Abstract

A stabilizing treatment agent for promoting the formation of a dense and stable rust layer on weathering steel, comprising a promoter and a slow-release agent, the promoter comprising Cu 2+ salt 0.5-5 wt%, Fe 2+ salt 0.5-5 wt%, SO4 2‑ salt 0.5-10 wt%, Cl ‑ salt 0.01-15% wt%; the slow-release agent comprising MoO4 2‑ salt 0-4 wt%, HPO4 2‑ salt 0-3 wt% and CaCl2 0-4 wt%, the remainder being a solvent. The promoter in the present invention, which initially comprises Cu 2+ salt, Fe 2+ salt, SO4 2‑ salt, Cl ‑ salt, promotes the rapid formation of a rust layer on the surface of weathering steel, and then the addition of a corrosion inhibitor comprising MoO4 2‑ salt, HPO4 2‑ salt or CaCl2 can form insoluble precipitates with the promoter added earlier in the rust layer, and the insoluble precipitates can fill in the defects in the rust layer, promoting a denser rust layer and accelerating the densification of the rust layer. Therefore, under the synergistic effect of the soluble salts of the promoter and the slow-release agent, uniform corrosion of the surface of weathering steel can be promoted, a dense and stable protective rust layer can be rapidly formed, and the problems of poor rust layer stability, high requirements for rust layer formation, and complex preparation of the stabilizing treatment agent in the prior art are solved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of surface pretreatment of weathering steel, and more particularly relates to a stabilizing treatment agent for promoting the formation of a dense and stable rust layer of weathering steel. BACKGROUND

[0002] Weathering steel (atmospheric corrosion resistant steel) is a kind of low alloy steel with excellent corrosion resistance by adding a small amount of corrosion-resistant elements such as copper and chromium in plain carbon steel. In the natural environment, weathering steel can use the protective stable rust layer generated by itself to prevent further corrosion, thereby achieving bare use. The bare use of weathering steel not only omits the traditional painting process, but also is maintenance-free in the later stage, significantly reducing the use cost of steel structure. Therefore, the paint-free application of weathering steel has become a new trend in the field of steel structure construction at home and abroad.

[0003] However, it takes a relatively long time (usually more than 3 years) for weathering steel to completely generate a stable rust layer in the atmospheric environment, which leads to the phenomenon of rust liquid hanging and flying and polluting the environment at the initial stage of bare use of weathering steel, and seriously affects the consistency of the appearance color of weathering steel. In addition, in coastal or high temperature and high humidity areas, it is difficult to form a protective rust layer. This seriously limits the promotion of the paint-free application of weathering steel. To solve this problem, in the 1950s, Japan first proposed to perform a stabilizing treatment on the surface of weathering steel, that is, to pretreat the surface of weathering steel before service, so as to shorten the formation period of the stable rust layer, thereby achieving the purpose of "preventing rust with rust" and preventing environmental pollution caused by rust liquid hanging and flying.

[0004] The existing weathering steel rust layer stabilizing treatment technology mostly adopts film coating treatment, that is, the surface of the weathering steel component is pretreated before use, so as to shorten the formation process of the stable rust layer of the weathering steel. It can not only avoid the phenomenon of yellow rust liquid hanging flow at the initial stage of use of weathering steel, prevent pollution, but also form a stable protective rust layer. For example, CN202010622722.6 A weathering steel rust layer stabilizing treatment agent and its use method discloses a formula of using 20% to 40% of epoxy resin modified polyvinyl alcohol, 0.5% to 4% of nickel sulfate, 2% to 5% of copper phosphate, 0.5% to 4% of sodium molybdate, 5% to 15% of iron red, and the rest is water, for surface rust layer stabilizing treatment of weathering steel, which can prevent rust liquid hanging and flying on the surface of weathering steel and accelerate the formation of a stable rust layer on the surface of weathering steel. However, the copper phosphate in the patent needs to be adjusted to be acidic by adjusting the pH value of the solution to play a role, the rust layer formation environment is high, and the epoxy resin modified polyvinyl alcohol needs to be heated at high temperature, so the preparation steps are complex, and therefore it is not conducive to actual production and application. SUMMARY

[0005] In order to overcome the above-mentioned existing weathering steel rust layer stability is poor, rust layer formation requirements high and stable treatment agent preparation complex, provide a kind of stable treatment agent for promoting the formation of dense stable rust layer of weathering steel.

[0006] The present application is realized by the following technical solutions:

[0007] A kind of stable treatment agent for promoting the formation of dense stable rust layer of weathering steel, including accelerator and slow-release agent, the accelerator includes Cu 2+ Salt 0.5-5wt%, Fe 2+ Salt 0.5-5wt%, SO4 2- Salt 0.5-10wt%, Cl - Salt 0.01-15wt%;Slow-release agent includes MoO4 2- Salt 0-4wt%, HPO4 2- Salt 0-3wt% and CaCl20-4wt%, the rest is solvent.The accelerator and slow-release agent in the application are all soluble salt, and a relatively dense stable protective rust layer can be quickly generated on the surface of weathering steel by using two-step spraying method.

[0008] Cl - In the accelerator, it can penetrate the passivation film and quickly initiate corrosion.SO4 2- Can reduce the pH value of liquid film reaction, accelerate the initial corrosion rate of weathering steel, and also promote the generation of α-FeOOH.Cu 2+ Can promote the formation of more stable spinel oxide CuFeO2, which can repair the defects of rust layer and make the rust layer have cation selectivity.Fe 2 + Can promote the formation of γ-FeOOH, thereby accelerating the generation of α-FeOOH.As the accelerator can promote the rapid corrosion of the surface of weathering steel, and the initial rust layer grows continuously to produce internal stress, which can cause cracks and holes in the rust layer, so that the initial generated rust layer is loose and porous, and the effect of alloy elements is gradually exerted, so slow-release agent needs to be added.

[0009] Ca 2+ In the corrosion inhibitor, not only can reduce the porosity of the rust layer, but also can accelerate the penetration of Cu element, further play the role of Cu element enrichment in the rust layer.In addition, CaSO4 precipitate will be formed, which will adhere to the surface of steel matrix and hinder the corrosion of corrosive medium, thereby playing a slow-release role.HPO4 2- Can form a hardly soluble phosphate with Fe 2+ In the process of steel anode dissolution, promote the formation of phosphating film.MoO4 2- With Fe 2+The reaction occurs to generate the insoluble FeMoO4 which exists in the rust layer, inhibits the anode dissolution and plays the role of slow-release protection.

[0010] Further, the accelerator includes Cu 2+ salt includes one or more of CuSO4, CuCl2, Cu(NO3)2; Fe 2+ salt includes one or more of FeSO4, FeCl2, Fe(NO3)2; SO4 2- salt includes one or more of CuSO4, FeSO4; Cl - salt includes one or more of NaCl, CuCl2, FeCl2.

[0011] Further, the slow-release agent includes MoO4 2- salt includes one or more of Na2MoO4, K2MoO4; HPO4 2- salt includes one or more of Na2HPO4, (NH4)2HPO4, K2HPO4.

[0012] Further, the accelerator further includes Cr 3+ salt, NaHSO3, one or both of the Cr 3+ salt includes one or more of Cr2(SO4)3, Cr(NO3)3, CrCl3.

[0013] Cr 3+ enriches in the rust layer and can gradually replace some positions of Fe 3+ in the α-FeOOH so as to transform into the α-(Fe 1-x Cr x )OOH with a smaller size even at the nanometer level. Thus, the transformation of the α-FeOOH is promoted, the crystal grains are refined, the rust layer is more compact and the invasion of the corrosion medium is blocked.

[0014] HSO3 - with strong reducibility accelerates the chemical corrosion process of the weathering steel surface, promotes the uniform corrosion of the weathering steel surface and is beneficial to the generation of the uniform rust layer.

[0015] Preferably, the accelerator includes 0.5-5wt% CuSO4, 0.5-5wt% FeSO4, 0.01-2wt% NaCl and the rest is solvent.

[0016] Preferably, the slow-release agent includes one or both of 0-4wt% Na2MoO4, 0-4wt% CaCl2, 0-3wt% Na2HPO4 and the rest is solvent.

[0017] Preferably, the accelerator further comprises one or both of 0-2wt% NaHSO3 and 0-3wt% Cr2(SO4)3.

[0018] Further preferably, the accelerator comprises 0.5-1wt% CuSO4, 0.5-1wt% FeSO4, 0-0.1wt% NaHSO3, 0.01-0.1wt% NaCl, 0-1wt% Cr2(SO4)3, the corrosion inhibitor comprises 0-1wt% Na2MoO4, 0-1wt% CaCl2 and 0-0.5wt% Na2HPO4, and the rest is solvent.

[0019] Further preferably, the accelerator raw material comprises: 0.6wt% CuSO4, 0.6wt% FeSO4, 0.06wt% NaHSO3, 0.03wt% NaCl, the corrosion inhibitor is 0.5wt% CaCl2, and the rest is solvent.

[0020] Further, the solvent is one of water, an ethanol aqueous solution, a mixture of water and a water-soluble resin, and a mixture of a resin dissolved in ethanol.

[0021] Further, the step of applying the above-mentioned stabilizing treatment agent to the surface of the weathering steel comprises:

[0022] S1. Preparation of the stabilizing treatment agent: according to the proportioning of each raw material of the accelerator, the raw material is uniformly dispersed in an aqueous solution to obtain the accelerator; and according to the proportioning of each raw material of the corrosion inhibitor, the raw material is uniformly dispersed in an aqueous solution to obtain the corrosion inhibitor;

[0023] S2. The prepared accelerator is first uniformly sprayed on the surface of the weathering steel, and then the corrosion inhibitor is uniformly sprayed on the surface of the weathering steel, so that the weathering steel is kept wet for 12-24h, and then dried; the above steps are repeated for 3-5 times to obtain a protective rust layer with uniform coverage.

[0024] Compared with the prior art, the beneficial effects are:

[0025] The present application first promotes the weathering steel surface to rapidly generate a rust layer by means of an accelerator containing Cu 2+ salt, Fe 2+ salt, SO4 2- salt and Cl - salt, and then adds a corrosion inhibitor containing MoO4 2- salt, HPO4 2- salt or CaCl2 to form a hardly soluble precipitate with the accelerator in the rust layer, so that the hardly soluble precipitate can fill the defects of the rust layer and promote the rust layer to be more dense and accelerate the densification of the rust layer. Therefore, under the synergistic effect of the accelerator and the corrosion inhibitor, the weathering steel surface can be uniformly corroded and a dense and stable protective rust layer can be rapidly formed.

[0026] The present application also adds HSO3 - , Cr 3+ and the like, further enhancing the effect of the accelerant. More specifically, NaHSO3 can provide HSO3 - with strong reducing property, accelerating the process of chemical corrosion on the surface of weathering steel, promoting uniform corrosion on the surface of weathering steel, and being conducive to the formation of uniform rust layer. Cr2(SO4)3 can provide Cr 3+ , and the enrichment of Cr element in the rust layer can gradually replace some positions of Fe 3+ in α-FeOOH, thereby converting into α-(Fe 1-x Cr x )OOH with even smaller size or even nanoscale. Thus, the conversion of α-FeOOH is promoted, the grain is refined, and the rust layer is more compact, thereby blocking the invasion of corrosive medium.

[0027] The weathering steel treated by the stabilizer according to the present application is more uniform in corrosion during use, the rust layer has more beautiful color, meanwhile, the loss of rust liquid is prevented, the phenomenon of rust liquid dripping is avoided, and the pollution to the environment is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 Figure 1 is the cross-sectional morphology of the rust layer of the weathering steel without surface stabilization treatment after dry / wet alternating accelerated corrosion for 64 days in the embodiment of the present application.

[0029] Figure 2 Figure 2 is the cross-sectional morphology of the rust layer of the weathering steel with surface stabilization treatment after dry / wet alternating accelerated corrosion for 64 days in Example 1 of the present application.

[0030] Figure 3 Figure 3 is the cross-sectional morphology of the rust layer of the weathering steel with surface stabilization treatment after dry / wet alternating accelerated corrosion for 64 days in Example 2 of the present application.

[0031] Figure 4 Figure 4 is the cross-sectional morphology of the rust layer of the weathering steel with surface stabilization treatment after dry / wet alternating accelerated corrosion for 64 days in Example 3 of the present application.

[0032] Figure 5 Figure 5 is the cross-sectional morphology of the rust layer of the weathering steel with surface stabilization treatment after dry / wet alternating accelerated corrosion for 64 days in Example 4 of the present application.

[0033] Figure 6 Figure 6 is the cross-sectional morphology of the rust layer of the weathering steel with surface stabilization treatment after dry / wet alternating accelerated corrosion for 64 days in Example 5 of the present application.

[0034] Figure 7Rust layer surface morphology of surface treated and untreated weathering steels after 64 days of dry / wet alternating accelerated corrosion.

[0035] Figure 8 Polarization curves of surface treated and untreated weathering steels after 64 days of dry / wet alternating accelerated corrosion.

[0036] Figure 9 Open circuit potential curves of surface treated and untreated weathering steels after stabilization. DETAILED DESCRIPTION

[0037] The application will be further explained and illustrated with reference to the following examples, which are not intended to limit the application in any way. Unless otherwise indicated, the methods and materials used in the examples are conventional methods and materials used in the art, and the materials used are commercially available.

[0038] Example 1

[0039] The present example provides an application of a stabilizing treatment agent for promoting the formation of a dense and stable rust layer on weathering steels, comprising the following steps:

[0040] S1. Preparation of the accelerator: uniformly disperse 0.6% CuSO4, 0.6% FeSO4, and 0.03% NaCl in water to obtain the accelerator. Preparation of the corrosion inhibitor: uniformly disperse 0.5% CaCl2 in water to obtain the corrosion inhibitor.

[0041] S2. First, spray the prepared accelerator on the surface of the weathering steel after removing the surface oxide scale, and then uniformly spray the corrosion inhibitor. Place the weathering steel in a salt spray corrosion test chamber to keep it moist for 12 hours, and then place it in a drying oven for 12 hours. Repeat the above steps 4 times until a uniform protective rust layer is obtained.

[0042] Example 2

[0043] The present example provides an application of a stabilizing treatment agent for promoting the formation of a dense and stable rust layer on weathering steels, comprising the following steps:

[0044] S1. Preparation of the accelerator: uniformly disperse 0.6% CuSO4, 0.6% FeSO4, 0.03% NaCl, and 0.06% NaHSO3 in water to obtain the accelerator. Preparation of the corrosion inhibitor: uniformly disperse 0.5% CaCl2 in water to obtain the corrosion inhibitor.

[0045] S2. First, the prepared accelerator is sprayed on the surface of the weathering steel after removing the surface scale and wiping with anhydrous ethanol and blowing dry with cold air, then the corrosion inhibitor is uniformly sprayed, and it is placed in a salt spray corrosion test box to keep it wet for 12 h and then placed in a drying oven for 12 h. Repeat the above steps 4 times until a uniform protective rust layer is obtained.

[0046] Example 3

[0047] This example provides an application of a stabilizing treatment agent for promoting the formation of a dense and stable rust layer on weathering steel, the steps comprising:

[0048] S1. Preparation of the accelerator: uniformly disperse 0.6% CuSO4, 0.6% FeSO4, 0.03% NaCl, 0.06% NaHSO3, and 0.5% Cr2(SO4)3 in an aqueous solution to obtain the accelerator. Preparation of the corrosion inhibitor: uniformly disperse 0.5% CaCl2 in an aqueous solution to obtain the corrosion inhibitor.

[0049] S2. First, the prepared accelerator is sprayed on the surface of the weathering steel after removing the surface scale and wiping with anhydrous ethanol and blowing dry with cold air, then the corrosion inhibitor is uniformly sprayed, and it is placed in a salt spray corrosion test box to keep it wet for 12 h and then placed in a drying oven for 12 h. Repeat the above steps 4 times until a uniform protective rust layer is obtained.

[0050] Example 4

[0051] This example provides an application of a stabilizing treatment agent for promoting the formation of a dense and stable rust layer on weathering steel, the steps comprising:

[0052] S1. Preparation of the accelerator: uniformly disperse 0.6% CuSO4, 0.6% FeSO4, 0.03% NaCl, 0.06% NaHSO3, and 0.5% Cr2(SO4)3 in an aqueous solution to obtain the accelerator. Preparation of the corrosion inhibitor: uniformly disperse 0.5% CaCl2 in an aqueous solution to obtain the corrosion inhibitor.

[0053] S2. First, the prepared accelerator is sprayed on the surface of the weathering steel after removing the surface scale and wiping with anhydrous ethanol and blowing dry with cold air, then the corrosion inhibitor is uniformly sprayed, and it is placed in a salt spray corrosion test box to keep it wet for 12 h and then placed in a drying oven for 12 h. Repeat the above steps 4 times until a uniform protective rust layer is obtained.

[0054] Example 5

[0055] This example provides an application of a stabilizing treatment agent for promoting the formation of a dense and stable rust layer on weathering steel, the steps comprising:

[0056] S1. Preparation of the accelerator: 0.6% CuSO4, 0.6% FeSO4, 0.03% NaCl, 0.06% NaHSO3, 0.5% Cr2(SO4)3, all by mass, were uniformly dispersed in an aqueous solution to obtain the accelerator. Preparation of the corrosion inhibitor: 0.5% Na2MoO4, by mass, was uniformly dispersed in an aqueous solution to obtain the corrosion inhibitor.

[0057] S2. The prepared accelerator was first sprayed on the surface of the weathering steel after removal of the surface scale, scrubbing with anhydrous ethanol, and drying with cold air. Then the corrosion inhibitor was uniformly sprayed, and the sample was placed in a salt spray corrosion test chamber to keep it moist for 12 h, and then dried in a drying oven for 12 h. The above steps were repeated 4 times until a uniform protective rust layer was obtained.

[0058] Experimental Example

[0059] The bare steel surface of the weathering steel without any treatment was used as the untreated sample for comparison. The weathering steel after surface stabilization treatment and the weathering steel without surface treatment (comparison sample) were subjected to accelerated corrosion test by dry / wet alternating corrosion test (drying for 12 h, moistening for 12 h). The sprayed sample was placed in a salt spray test chamber for a set time (24 h) to verify whether the weathering steel after surface stabilization treatment could uniformly rust and prevent the loss of rust liquid under accelerated corrosion conditions. The corrosion medium was 0.03 mass% NaCl, the temperature of the test chamber was (30±2)℃, the humidity was controlled within (70±5)%, and the duration of the entire experiment was 64 d.

[0060] Cl-in the accelerator can penetrate the passivation film and quickly initiate corrosion. SO4 2- can reduce the pH value of the liquid film reaction, accelerate the initial corrosion rate of weathering steel, and promote the formation of α-FeOOH. Cu 2+ can promote the formation of more stable spinel oxide CuFeO2 in the rust layer, enriches at the crack of the rust layer to repair the defects of the rust layer, and makes the rust layer have cation selectivity. Fe 2+ can promote the formation of γ-FeOOH, thereby accelerating the formation of α-FeOOH. NaHSO3 can provide HSO3 - , which can accelerate the chemical corrosion process of the surface of weathering steel, promote uniform corrosion of the surface of weathering steel, and be beneficial to the formation of uniform rust layer. Cr2(SO4)3 can provide Cr 3+ , and the enrichment of Cr element in the rust layer can gradually replace some positions of Fe 3+ in α-FeOOH to transform into α-(Fe 1-x Cr xOOH. Thus, the conversion of α-FeOOH is promoted, the crystal grains are refined, and the rust layer is more compact to block the invasion of corrosive media.

[0061] Ca 2+ Not only can reduce the porosity of rust layer but also accelerate the penetration of Cu element, further play the role of Cu element in the enrichment of rust layer. In addition, CaSO4 precipitate will be formed, which will adhere to the surface of steel matrix, hinder the corrosion of corrosive medium, thus play a slow-release effect. 2 - can be dissolved in the process of steel anode with Fe 2+ Forming a difficult soluble phosphate, promote the formation of phosphating film. MoO4 2- Reaction with Fe 2+ Anode dissolution, slow-release protection effect.

[0062] As Figure 1 The untreated weathering steel after 64 days of accelerated corrosion, the rust layer exists a large number of cracks and holes, and the crack gap of the inner and outer rust layer is large.

[0063] As Figure 2 The weathering steel treated by stabilizer after 64 days of accelerated corrosion, the outer rust layer is relatively loose, and there is a cavity part, the inner rust layer exists a small amount of microcracks, but the overall rust layer is continuous and dense.

[0064] As Figure 3 The treated weathering steel rust layer is continuous and dense without obvious defects.

[0065] As Figure 4 The treated weathering steel rust layer is continuous and dense with better protection ability.

[0066] As Figure 5 The treated weathering steel outer rust layer is relatively uniform and dense, and the overall rust layer has better protection ability

[0067] As Figure 6 The treated weathering steel inner rust layer is thicker and more dense and uniform.

[0068] As Figure 7 The untreated weathering steel after 64 days of accelerated corrosion, the rust layer surface is severely corroded and uneven, many loose rust layers are gradually destroyed and fall off, and the overall surface is broken. The overall rust layer of the weathering steel treated by stabilizer is relatively flat and uniform, and has good adhesion with the matrix.

[0069] As Figures 8-9As shown, the rust layer of the weathering steel after the stabilization treatment has a higher self-corrosion potential, and the weathering steel after the stabilization treatment has a higher OCP value in the whole corrosion process, indicating that it has better corrosion resistance.

[0070] Obviously, the above-mentioned embodiments of the present application are only examples for clearly illustrating the present application, and are not intended to limit the implementation modes of the present application. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. Here, all the implementation modes are not required or can not be exhausted. Any modification, equivalent replacement and improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the claims of the present application.

Claims

1. A method for applying a stabilizing agent that promotes the formation of a dense and stable rust layer on weathering steel, characterized in that, The stabilizing agent includes an accelerator and a slow-release agent. The accelerator comprises: 0.6% CuSO4, 0.6% FeSO4, 0.03% NaCl, 0.06% NaHSO3, and 0.5% Cr2(SO4)3. The corrosion inhibitor is 0.5wt% CaCl2, and the remainder is a solvent. The steps for applying it to the surface of weathering steel include: S1. Preparation of stabilizing agent: According to the ratio of each raw material of the accelerator, it is uniformly dispersed in the solvent to obtain the accelerator; according to the ratio of each raw material of the slow-release agent, it is uniformly dispersed in the solvent to obtain the slow-release agent; S2. First, spray the prepared accelerator evenly on the surface of the weathering steel, then spray the corrosion inhibitor evenly on the surface of the weathering steel, keep it moist for 12~24 hours, and then dry it to obtain a uniformly covered protective rust layer.

2. The method of applying the stabilizing agent for promoting the formation of a dense and stable rust layer on weathering steel according to claim 1, characterized in that, Its features are, The solvent is water or an aqueous solution of ethanol.

3. The method of applying the stabilizing agent for promoting the formation of a dense and stable rust layer on weathering steel according to claim 1, characterized in that, Repeat steps S1 and S2 3-5 times.

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