Reinforcing and protecting treatment method for rusty fragile iron cultural relics

Abstract

The invention discloses a reinforcement protection treatment method for rusty fragile iron cultural relics, and belongs to the technical field of metal cultural relic protection. The method comprises the following steps: firstly, carrying out permeation treatment on a corrosion layer by adopting reinforcing liquid, and synergistically improving the compactness of the corrosion layer and the bonding strength among particles by utilizing in-situ filling of a newly generated rust product and induced regrowth of an original corrosion product; and then a compound alcohol of ethanol, ethylene glycol and 1, 2-propylene glycol is used as a solvent system, a polyhydroxy cooperative regulation strategy is introduced into hydrolysis-polycondensation kinetics and film forming behavior control of hexadecyl trimethoxy silane, hydrophobic sealing is performed on a reinforced corrosion layer, and the surface is endowed with long-term stable corrosion resistance. According to the method, ferrous ion source in-situ reinforcement and a compound alcohol regulation and control organic silicon hydrophobic film forming technology are synergistically applied to protection of rusty fragile iron cultural relics for the first time, the treatment process is mild and controllable, secondary damage is avoided, the method highly conforms to the cultural relic protection principle of repairing old as old and keeping the original appearance, and the method is simple and convenient in process, low in cost, high in universality and suitable for industrial production. The method can be widely applied to reinforcement and protection treatment of various unearthed, water-discharged and propagated fragile rusty iron cultural relics.

Description

Technical Field

[0001] This invention belongs to the field of cultural relic protection technology, specifically involving a method for strengthening fragile rusty iron cultural relics by using an iron ion source consolidation liquid, optimizing the dispersion effect of silane coupling agents and improving the stability of the film layer by compounding alcohol solvents, and finally realizing the protection of fragile rusty iron cultural relics. Background Technology

[0002] Ironware, as an important part of China's historical and cultural heritage, possesses extremely high historical, artistic, and scientific value. In fact, whether excavated, recovered from underwater, or still in existence, ironware often exhibits signs of complete or severe corrosion. For example, ironware recovered from the "Nanhai No. 1" shipwreck is completely mineralized, with only rusted outlines remaining; Han Dynasty ironware unearthed by the Wuxi Archaeological Institute is corroded and powdery, its structure on the verge of disintegration; and the iron components of the Weiyuan miniature train show severe surface mineralization and layered peeling. How to protect these fragile ironware pieces while they are rusted has attracted considerable attention.

[0003] These types of rusty and fragile iron artifacts generally exhibit complex porous structures and multi-layered corrosion characteristics: the outer layer is loose and easily detachable harmful rust; the middle layer often contains metastable transitional corrosion products; and the inner layer commonly contains highly hygroscopic and autocatalytically corroding "powdery rust," which continuously penetrates into the substrate, causing the artifact to crumble, perforate, or even collapse entirely. Simultaneously, their porous structure makes it difficult for conventional protective materials to form a complete coating. A single solvent system can only cover the surface and cannot penetrate deep into the pores, leaving corrosive media within. Furthermore, the air and residual corrosive media within the pores hinder the formation of a protective film, leading to discontinuous film layers, poor adhesion, and rapid failure of the protective effect.

[0004] In recent years, metal artifact preservation technology has made some progress. For example, Wu Simin et al. constructed an organosilicon hydrophobic film on the simulated bronze surface using the sol-gel method, using low surface energy materials to reduce water erosion; patent CN119735971A used organosilicon-modified micro-nano silica precursor liquid to achieve corrosion inhibition and sealing of metal artifact surfaces; patent CN103694425A disclosed a TiO2 particle-modified acrylate composite coating to enhance the surface stability of artifacts. However, the above methods are mostly aimed at the surface protection of dense metal substrates, and have obvious limitations for fragile iron artifacts that have been severely mineralized, loose and porous: (1) the protective material is difficult to penetrate deep into the pores and cannot effectively solidify and isolate the powdery rust area; (2) the film is prone to cracking and falling off after formation, and has poor compatibility with the mineralized interface; (3) the processing involves heating or strong solvents, which can easily cause secondary damage to the fragile substrate; (4) there is a lack of in-situ reinforcement of the iron substrate itself.

[0005] "Restoring the old as it was and maintaining its original appearance" is a basic principle of cultural relic protection. Therefore, it is urgent to develop a pretreatment technology that can effectively enhance the structural strength of fragile iron cultural relics, has corrosion-inhibiting function, and has a gentle and controllable treatment process, so as to break through the existing protection bottleneck. Summary of the Invention

[0006] To address the significant shortcomings of existing conservation technologies for rusty and fragile iron artifacts in terms of structural reinforcement and infiltration sealing, this invention provides a mild, controllable, safe, and efficient method for strengthening and protecting rusty and fragile iron artifacts. This method uses a reinforcing solution to provide in-situ strength reinforcement to the mineralized rust layer, and combines a compound alcohol system to optimize the film-forming properties of organosilicon, simultaneously achieving structural reinforcement and corrosion protection of the iron artifact. This effectively avoids problems such as cracking, powdering, and film peeling that are easily caused by traditional treatments, providing an innovative protection path for severely mineralized, porous, and corroded iron artifacts that combines structural stability and interface compatibility.

[0007] To achieve the above objectives, the technical solution adopted by the present invention includes the following steps:

[0008] Step 1: Preparation and use of reinforcement fluid

[0009] L-Ascorbic acid was added to an aqueous citric acid solution and stirred until completely dissolved. FeCO3 powder was then added, and stirring continued until the system turned a uniform light green color. After standing, the supernatant was collected, yielding a consolidation solution with a ferrous ion concentration of 0.1–0.4 mol / L. The rusty, fragile iron artifact was completely immersed in the consolidation solution, ensuring no area was exposed to air. The artifact was simultaneously secured with a support to prevent direct contact with the container walls. After soaking for 10–15 minutes, the iron artifact was removed and placed in a forced-air drying oven to dry, completing one soaking-drying treatment. This soaking-drying treatment was repeated until the weight of the iron artifact no longer increased, yielding the pretreated iron artifact.

[0010] Step 2: Preparation and use of compound alcohol hydrolysate

[0011] Ethanol, ethylene glycol, 1,2-propanediol, and ultrapure water were thoroughly mixed to prepare a compound alcohol solvent, wherein the volume ratio of ethanol, ethylene glycol, and 1,2-propanediol in the compound alcohol solvent was 3–7:1:0–1. Hexadecyltrimethoxysilane was added dropwise to the compound alcohol solvent, and citric acid was added to adjust the pH to 4–6. The mixture was stirred to hydrolyze the solution, yielding a hydrolysate. The pretreated iron artifact was completely immersed in the hydrolysate for 10–15 minutes, then removed and allowed to air dry at room temperature to obtain a securely protected iron artifact.

[0012] In step 1 above, the concentration of the citric acid aqueous solution is preferably 0.1 to 0.2 mol / L.

[0013] In step 1 above, the preferred molar ratio of citric acid to L-ascorbic acid is 1:0.03 to 0.05.

[0014] In step 1 above, the preferred molar ratio of FeCO3 to citric acid is 1:0.2 to 0.5.

[0015] In step 1 above, it is preferable to dry the soaked iron artifact sample in a forced-air drying oven at 20-40 ℃ for 6-10 h.

[0016] In step 2 above, preferably, the volume ratio of ethanol, ethylene glycol, and 1,2-propanediol in the compound alcohol solvent is 5:1:1.

[0017] In step 2 above, the preferred volume ratio of the total volume of ethanol, ethylene glycol, and 1,2-propanediol to ultrapure water is 4 to 9:1.

[0018] In step 2 above, the preferred volume ratio of the compounded alcohol solvent to hexadecyltrimethoxysilane is 5 to 10:1.

[0019] In step 2 above, it is preferable to stir and hydrolyze at 35–50 °C for 4–6 h.

[0020] The beneficial effects of this invention are as follows:

[0021] 1. This invention employs a reinforcing solution to penetrate and treat the rust layer of brittle iron artifacts. It utilizes a dual mechanism of in-situ filling by newly generated iron oxide microcrystals and induced regrowth of existing rust products to synergistically enhance the density and interparticle bonding strength of the rust layer, achieving internal structural reinforcement rather than merely surface sealing. The treatment process adopts a "circulating immersion-drying" mode, using the cessation of weight increase in the artifact as the endpoint of reinforcement, ensuring full process control and avoiding over-treatment or under-reinforcement, exhibiting good operability and reproducibility. The microcrystalline products generated after reinforcement are three typical iron oxides: α-FeOOH, Fe3O4, and Fe2O3, highly compatible with the original rust components of the artifact. The crystal grain length is concentrated in the range of 7–10 μm, and the width in the range of 2–5 μm, with uniform distribution and regular morphology, facilitating the formation of a dense and stable reinforcing layer. The reinforcing solution is a weakly acidic aqueous solution, and the entire process is conducted at room temperature without heating, strong solvents, or violent reactions, causing no secondary damage to the fragile mineralized matrix and strictly adhering to the principle of "minimal intervention" in artifact preservation.

[0022] 2. This invention breaks through the limitations of traditional protective materials that only focus on surface sealing or corrosion inhibition. It is the first to propose using ferrous ions as an active source to induce in-situ growth of iron oxide microcrystals within the rust layer, achieving active repair of the mineralized rust layer's own structural strength. In the rust microenvironment, ferrous ions can both deposit in-situ to fill pores (filling effect) and act as seed crystals to induce the continued growth of adjacent rust product crystals (regeneration effect), synergistically improving the mechanical properties and interfacial bonding of the rust layer. A mild coordination-reduction system is constructed using citric acid as a ligand, L-ascorbic acid as an antioxidant, and FeCO3 as the ferrous source, stably providing highly active ferrous ions, effectively inhibiting rapid oxidation and failure of ferrous ions, and ensuring continuous and efficient reinforcement. Conventional soaking operations are upgraded to a cyclical treatment process centered on penetration and crystallization. By repeatedly introducing the ferrous ion source and controlling the drying and crystallization conditions, microcrystals gradually grow, fill, and compact within the rust layer pores, ultimately forming a composite reinforcement layer with both physical reinforcement and chemical stability. This invention is highly original in terms of reinforcement concept, mechanism of action, and process implementation, opening up a new path for the structural stability protection of severely mineralized and fragile iron cultural relics.

[0023] 3. This invention employs a compound alcohol solvent system of ethanol, ethylene glycol, and 1,2-propanediol. For the first time, a multi-hydroxyl synergistic regulation strategy is introduced into the hydrolysis-condensation kinetics and film-forming behavior control of hexadecyltrimethoxysilane, effectively overcoming the inherent defects of single ethanol solvent, such as excessively rapid evaporation, insufficient wettability, limited penetration depth, and poor film uniformity. The hydroxyl groups contained in 1,2-propanediol can significantly accelerate the silane hydrolysis process, while ethylene glycol promotes the silanol condensation reaction through intermolecular hydrogen bonds. Simultaneously, its moderate viscosity and high boiling point endow the system with excellent leveling properties and evaporation inhibition capabilities. This compound system achieves precise control of the solvent evaporation rate from both physical and chemical perspectives: on the one hand, the high-boiling-point component delays solvent evaporation, avoiding pinholes, cracks, and film discontinuities caused by premature surface solidification; on the other hand, the suitable viscosity range ensures that the hydrolysate spreads evenly and flows fully on the complex morphology of iron artifacts, preventing sagging and local accumulation. Furthermore, the hydrogen bond network formed between the hydroxyl groups and silanols effectively buffers the rate of condensation reaction, reduces internal stress in the film, enhances flexibility, and significantly inhibits the self-polymerization tendency of silane intermediates, thereby improving the storage stability of the system. Thus, this compound alcohol solvent system ensures that the hydrolysate can deeply penetrate into the micropores, cracks, and mineralization interfaces of the rust layer of cultural relics, providing a dense and continuous functional layer foundation for subsequent chemical bonding and structural strengthening.

[0024] 4. This invention constructs a pretreatment method for fragile iron artifacts by synergistically integrating in-situ reinforcement with ferrous ion sources and the regulation of silane hydrophobic film formation by compound alcohols. This method combines high permeability, strong interfacial adhesion, and long-term protective capabilities. It not only provides in-situ structural reinforcement to the mineralized rust layer, significantly improving its mechanical stability and resistance to environmental erosion, but also strictly adheres to the principles of "minimal intervention" and "restoring the old as it was" in artifact preservation, effectively avoiding secondary damage caused by insufficient penetration, film brittleness, or thermal expansion mismatch in traditional reinforcement materials. For rusty and fragile iron artifacts treated with this invention, deterioration phenomena such as cracking, powdering, and surface peeling after dehydration are fundamentally curbed. The integrity of the rust layer and interfacial adhesion are significantly improved, greatly extending the artifact's preservation life and exhibition period. This method has outstanding advantages such as simple process, strong universality, and controllable cost, providing a systematic solution for the protection of severely mineralized and fragile iron artifacts that combines theoretical innovation with engineering feasibility. Attached Figure Description

[0025] Figure 1 These are SEM images and EDX spectra of the products on the filter paper magnified at 400x (a) and 2000x (b).

[0026] Figure 2 This is an analysis diagram of the distribution characteristics of the particle size length (a) and particle size width (b) of the product microcrystals on the filter paper.

[0027] Figure 3 This is a Raman spectrum verification result of the product microcrystals on the filter paper.

[0028] Figure 4 shows the potentiodynamic polarization curves of a standard cast iron corrosion plate in a compound alcohol solvent hydrolysate.

[0029] Figure 5 These are electrochemical impedance spectroscopy plots of standard cast iron corrosion pads in a compound alcohol solvent hydrolysate. A and d are Nyquist plots (E represents measured data points, eF represents the fitted curve), b and e are logarithmic phase angle plots, and c and f are logarithmic amplitude plots.

[0030] Figure 6 This is a viscosity distribution diagram of different volume ratios of compound alcohol solvents at 25 °C.

[0031] Figure 7 shows the stress-strain curves of the original rusty iron pot fragment sample and the rusty iron pot fragment samples in Example 1 after 10, 20, and 30 cycles of cyclic soaking-drying treatment.

[0032] Figure 8 shows the elemental mapping distribution of the original rusty iron pot fragment sample (a) and the rusty iron pot fragment samples after 10 (b), 20 (c), and 30 (d) cycles of immersion-drying treatment in Example 1.

[0033] Figure 9 shows laser confocal scanning images and corresponding 3D images of the original rusty iron pot fragment sample (a) and the rusty iron pot fragment samples after 10 (b), 20 (c), and 30 (d) cycles of immersion-drying treatment in Example 1.

[0034] Figure 10 shows the infrared spectra of the original rusty iron pot fragments and the rusty iron pot fragments samples from Example 1 after 10, 20, and 30 cycles of cyclic soaking and drying.

[0035] Figure 11 shows photographs of the surface appearance of the original rusty iron pot fragment sample and the rusty iron pot fragment sample after stabilization and protection treatment in Example 1. In the figures, a is the original rusty iron pot fragment sample; b and c are the front and back of the original rusty iron pot fragment sample after being stored in a constant temperature and humidity chamber at 25°C and 80% humidity for 3 weeks, respectively; d is the original rusty iron pot fragment sample after being stored in a constant temperature and humidity chamber at 25°C and 80% humidity for 3 weeks, followed by storage at room temperature for 30 days; e is the rusty iron pot fragment sample after stabilization and protection treatment after being stored in a constant temperature and humidity chamber at 25°C and 80% humidity for 3 weeks; and f is the rusty iron pot fragment sample after stabilization and protection treatment after being stored in a constant temperature and humidity chamber at 25°C and 80% humidity for 3 weeks, followed by storage at room temperature for 30 days.

[0036] Figure 12 shows scanning electron microscope (SEM) images of the original rusted iron pot fragments and the rusted iron pot fragments after stabilization and protection treatment in Example 1. In the figures, a is the original rusted iron pot fragment, b is the rusted iron pot fragment after stabilization and protection treatment, c is the original rusted iron pot fragment after 3 weeks of storage in a constant temperature and humidity chamber at 25°C and 80% humidity, and d is the rusted iron pot fragment after 3 weeks of storage in a constant temperature and humidity chamber at 25°C and 80% humidity.

[0037] Figure 13 shows the color difference values ​​of the rusty iron pot fragment sample after the stabilization and protection treatment in Example 1.

[0038] Figure 14 The images show the Fourier transform infrared spectra of the original rusty iron pot fragments (a), the original rusty iron pot fragments stored in a constant temperature and humidity chamber at 25 ℃ and 80% humidity for 3 weeks (b), and the rusty iron pot fragments sample after the stabilization and protection treatment in Example 1 stored in a constant temperature and humidity chamber at 25 ℃ and 80% humidity for 3 weeks (c).

[0039] Figure 15 shows contact angle test photos of the rusty iron pot fragment sample (a) after stabilization and protection treatment in Example 1, and after being completely dried at room temperature and stored in a constant temperature and humidity chamber at 25 ℃ and 80% humidity for 4 weeks (b) and then stored at room temperature for 30 days after 4 weeks (c). Detailed Implementation

[0040] This invention first employs a reinforcing solution to penetrate the rust layer. The reinforcing solution is prepared as follows: L-ascorbic acid is added to an aqueous citric acid solution and stirred until completely dissolved. Then, FeCO3 powder is slowly added. During stirring, a significant reduction in solid particles is observed, accompanied by continuous bubble escape. Stirring continues until the system becomes a uniform light green color, at which point stirring is stopped. After standing, the supernatant is collected to obtain a reinforcing solution with a ferrous ion concentration of 0.1–0.4 mol / L. To preliminarily investigate the oxidative crystallization behavior of the reinforcing solution, a 0.2 mol / L ferrous ion concentration of the reinforcing solution is dropped onto a qualitative filter paper substrate and completely impregnated. The impregnated filter paper is then placed in a constant temperature and humidity chamber at 30 °C and 80% relative humidity to accelerate the oxidation of ferrous ions and the formation of hydrated iron oxides. Repeating the aforementioned treatment process, the results show that with increasing treatment cycles, a brownish-black deposit gradually forms on the filter paper surface, eventually completely covering the substrate. The microstructure of the sediments was observed using scanning electron microscopy (SEM), and their phase composition was analyzed by Raman spectroscopy to clarify the characteristics of the products formed by the oxidation and crystallization of ferrous ions on the carrier surface.

[0041] Figure 1 The images show the SEM morphology of the oxidation products on the filter paper substrate at magnifications of 400x and 2000x. Under low magnification, the products exhibit a relatively uniform distribution, forming a composite structure of a colloidal matrix and microcrystalline particles. Under high magnification, the microcrystals clearly precipitate and grow from the colloidal matrix, exhibiting typical heterogeneous nucleation characteristics. Combined with EDX analysis, C (38.1%), O (43.8%), and Fe (18.2%) were detected at 400x magnification, and C (36.6%), O (26.5%), and Fe (36.9%) were detected at 2000x magnification. The carbon signal mainly originates from the filter paper cellulose substrate. With increasing magnification and focusing on microcrystalline particles, the iron content significantly increases while the carbon content relatively decreases, confirming the spatial correspondence between the iron-rich region and the microcrystalline particles. This indicates that iron oxides have achieved heterogeneous nucleation and localized enrichment growth on the filter paper surface.

[0042] Table 1. Elemental composition of micro-regions

[0043]

[0044] Figure 2 Histograms and Gaussian fitting curves of the particle size distribution of microcrystals on the filter paper surface are presented. Statistical results show that the crystallite length is mainly concentrated in the range of 7–10 μm, and the width is concentrated in the range of 2–5 μm, exhibiting a concentrated particle size distribution and regular morphology. These quantitative results provide a quantitative basis at the microscopic morphology level for subsequent analysis of the crystal evolution and growth mechanism of ferrous ion-induced iron oxide crystallization.

[0045] Figure 3The Raman spectrum of the microcrystals on the filter paper surface clearly reflects the multiphase composition of the product. Among them, the 245 cm⁻¹ peak... -1 299 cm -1 386 cm -1 The characteristic peaks at 289 cm⁻¹ correspond to the out-of-plane bending vibration of OH, the bending vibration of Fe-OH, and the symmetric stretching vibration of Fe-O, respectively, confirming the presence of the α-FeOOH phase; -1 With 408 cm -1 The Raman shift at 663 cm⁻¹ basically matches the A1g and Eg vibrational modes of α-Fe₂O₃ and can be identified as a characteristic signal of hematite. -1 The strong peak at that location is attributed to the A1g vibrational mode in the Fe3O4 spinel structure, a typical characteristic peak of magnetite. These Raman characteristics indicate that the microcrystals formed on the filter paper surface are a multiphase iron oxide mixture system in which α-FeOOH, Fe3O4, and α-Fe2O3 coexist.

[0046] The above carrier model experiments show that the reinforcing liquid used in this invention can induce the formation of three types of iron oxide microcrystals—α-FeOOH, Fe3O4, and α-Fe2O3—on the surface of filter paper (cellulose simulated substrate). Their phase composition is highly compatible with the typical corrosion components of iron artifacts, and the crystal size distribution is concentrated and the morphology is regular. Considering the application scenarios in cultural relic preservation, it can be inferred that when the reinforcing liquid penetrates into the pores and mineralization interfaces of the actual corrosion layer of iron artifacts, ferrous ions can also undergo heterogeneous nucleation on the surface of the corrosion products. Through a dual mechanism of in-situ pore filling and inducing the regrowth of existing corrosion products, a dense reinforcing layer with good compatibility with the substrate is formed, thereby effectively improving the density of the corrosion layer and the interparticle bonding strength.

[0047] This invention further employs a complex alcohol solvent system of ethanol, ethylene glycol, and 1,2-propanediol to regulate the hydrolysis-condensation behavior of hexadecyltrimethoxysilane (HDTMS) and perform hydrophobic film formation treatment on the reinforced rust layer to achieve long-term stable anti-corrosion performance. The hydrolysate preparation method is as follows: Ethanol, ethylene glycol, 1,2-propanediol, and ultrapure water are added sequentially to a beaker at different volume ratios, wherein the fixed volumes of ethylene glycol and ultrapure water are both 10 mL, and the volumes of ethanol and 1,2-propanediol are adjusted according to a preset ratio; the mixture is magnetically stirred at 25 ℃ and 600 r / min for 10 min; then 10 mL of HDTMS is added dropwise, and the pH of the system is adjusted to 5.0 with citric acid; the temperature is raised to 40 ℃, and hydrolysis is carried out continuously at 600 r / min for 5 h to obtain a clear and homogeneous hydrolysate. Standard cast iron corrosion plates are suspended with nylon thread and completely immersed in the above hydrolysate. After soaking for 10 min, they are removed and dried vertically at room temperature. Polarization curves and electrochemical impedance spectroscopy (EIS) were performed on cast iron platings treated with different hydrolysates using an electrochemical workstation. The results are shown in Table 2 and [Table data missing]. Figure 4 .

[0048] Table 2. Polarization curves and corrosion parameters of cast iron hangers after treatment with hydrolysate of alcohol solvents with different volume ratios.

[0049]

[0050] Table 2 shows that the corrosion potential (E) of the untreated blank sample is... corr The value is -1100 mV vs. SCE, and the self-corrosion current density (I0) is... corr The value is 163.9 μA·cm. -2 After treatment with hydrolysates of different compound ratios, the E values ​​of all samples were... corr Both exhibited positive shifts, with amplitudes ranging from 32 to 71 mV vs. SCE; corr A significant decrease was observed, with a reduction of 121.1–144.4 μA·cm⁻¹. -2 Among them, when the volume ratio of ethanol, ethylene glycol, and 1,2-propanediol is 5:1:1, the corrosion inhibition efficiency reaches the highest value of 88.1%, corresponding to E corr Positive shift 71mV, I corr Reduced to 19.5 μA·cm -2 . Figure 4 The polarization curves show that the curves of each treatment group sample are similar to those of the blank sample (KB), and there is no obvious deformation of the cathode and anode branches. This indicates that the introduction of the compound alcohol solvent did not change the electrode reaction kinetics mechanism on the cast iron surface, and the corrosion inhibition effect is due to the physical barrier of the protective film on the corrosive medium rather than the change of the reaction path.

[0051] Table 3. Equivalent circuit parameters of cast iron hanging samples after hydrolysis with different volume ratios of alcohol solvent.

[0052]

[0053] EIS data were fitted using ZView software using equivalent circuits, and the electrochemical parameters are listed in Table 3. The film resistance (Rct) characterizes the coating's ability to block ion penetration, while the dispersion index n of the constant phase angle element (CPE) reflects the film uniformity and defect density. The fitting results show that the sample treated with the hydrolysate prepared by mixing ethanol, ethylene glycol, and 1,2-propanediol in a volume ratio of 5:1:1 had the highest Rct value among all groups, and its CPE parameters (especially the n value) were also significantly better than other ratios, with the n value approaching 1, indicating a smooth, dense film surface with few defects. Figure 5 The images show the EIS spectra of the samples. Nyquist plots (a, d) show that all samples exhibit a single capacitive arc. The arc radius of the treated samples significantly increased, with the 5:1:1 group showing the largest arc radius, which was further increased compared to the 5:1 group (ethanol: ethylene glycol) without 1,2-propanediol. In the logarithmic phase angle plots (b, e), the phase angle peak positions of each sample basically overlapped, and the peak widths were similar, indicating a consistent film formation mechanism. In the logarithmic amplitude plots (c, f), the 5:1:1 group exhibited the highest impedance modulus across the entire frequency range, showing stronger suppression capabilities, especially in the high and low frequency regions. This indicates that the film layer can effectively block charge transfer and significantly inhibit the diffusion process of corrosive media.

[0054] Figure 6 The viscosity distribution of different volume ratios of compound alcohol solvents at 25 °C is shown in the figure. As can be seen from the figure, the viscosity of ethanol alone is the lowest (1.07 mPa·s), and the viscosity gradually increases after the addition of ethylene glycol. When 1,2-propanediol is introduced and its ratio is adjusted, the viscosity of the system exhibits a regular change. The viscosity corresponding to a volume ratio of ethanol:ethylene glycol:1,2-propanediol of 5:1:1 is 8.89 mPa·s, which is within a suitable range—too low a viscosity can lead to excessively rapid evaporation and uneven film spreading; too high a viscosity results in poor penetration and retention defects. Under this viscosity condition, the hydrolysate can fully wet the cast iron surface and micropores while maintaining a sufficiently long liquid phase stability period, ensuring the orderly hydrolysis and condensation of silane molecules, ultimately forming a continuous, complete, and highly cross-linked protective film.

[0055] In summary, the optimal mixing ratio of ethanol, ethylene glycol, and 1,2-propanediol is 5:1:1. This system, by moderately increasing viscosity, extending evaporation time, and promoting silane crosslinking, synergistically enhances the film's density, uniformity, and adhesion, providing a comprehensive protection solution for fragile iron artifacts that combines penetration reinforcement and efficient sealing.

[0056] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0057] Example 1

[0058] Step 1: Preparation and use of iron ion source consolidation solution

[0059] Add 2.5 g (13 mmol) of citric acid to a beaker containing 100 mL of ultrapure water and stir magnetically at 400 r / min until completely dissolved to obtain a clear, colorless citric acid aqueous solution. Then add 0.1 g (0.6 mmol) of L-ascorbic acid and continue stirring until completely dissolved. While maintaining the stirring speed, slowly add 5 g (43 mmol) of analytical grade FeCO3 powder. During stirring, the solid particles decreased significantly, accompanied by continuous escaping of bubbles. Continue stirring until the system turns a uniform light green color, then stop stirring. After standing, collect the supernatant to obtain a consolidation solution with a ferrous ion concentration of 0.2 mol / L. Completely immerse the rusted iron pot fragment sample in the consolidation solution, ensuring that no area of ​​the sample is exposed to air. At the same time, fix the sample with a support to prevent it from directly contacting the beaker wall and ensure uniform immersion. After immersion for 10 min, remove the sample and place it in a 30℃ forced-air drying oven to dry for 8 h, completing one immersion-drying treatment. During the drying process, the sample needs to be fixed to ensure that its surface is in full contact with the hot air flow. After drying, the sample is directly transferred to a new consolidation solution for the next immersion without additional treatment. The above immersion-drying process is repeated. The weight of the sample is tested after each cycle. To ensure the repeatability of the test results, the average weight is calculated after each weighing three times. The results are shown in Table 4.

[0060] Table 4. Weight data of rusty iron pot fragments after different cycles of immersion-drying treatment.

[0061]

[0062] Observing the data in Table 4, it can be seen that the total weight of the sample gradually increased from the initial 2 g, reaching 2.1721 g after 25 cycles, and then stabilized at 2.1725 g after 26 cycles. The weight gain rate gradually decreased from 0.9% in the first cycle to 0.03% in the 25th cycle. The single weight gain steadily decreased from 0.0180 g (first cycle) to 0.0006 g (25th cycle). The weight gain in the first 10 cycles accounted for 68.5% of the total weight gain, and the final total weight gain was 0.1725 g, accounting for 8.625% of the total weight gain.

[0063] A comparative experiment was conducted between rusty iron pot fragment samples treated with the above-mentioned consolidation solution through cyclic immersion and drying, and the original rusty iron pot fragment samples (adjacent areas of the rusty iron pot fragment samples treated with the above-mentioned consolidation solution). Figure 7 As shown in Table 5, the rusty iron pot fragments were significantly strengthened after being soaked and dried in the strengthening solution, with the maximum compressive stress increasing from 15.69 MPa to 25.46–29.11 MPa.

[0064] Table 5 Stress-strain data of rusted iron pot fragments

[0065]

[0066] Depend on Figure 8 It is evident that the original sample of the rusty iron pot fragments was porous and rough. After being soaked and dried in a consolidation solution, the pores and cracks on the surface of the rusty iron pot fragments were gradually filled, and the distribution of O and Fe elements gradually became more uniform. Figure 9 As shown in Table 6, the surface roughness of the sample decreased significantly with the increase of the number of immersions, and the maximum height decreased from 96.604 μm to 43.318 μm.

[0067] Table 6 Surface roughness parameters of rusty iron pot fragments

[0068]

[0069] Figure 10 In the middle, FT-IR spectral analysis showed that at 477 cm⁻¹ -1 The characteristic peaks of Fe-O are attributed to the bending vibration peaks of Fe2O3; 562 cm⁻¹ -1 The characteristic peaks of Fe-O are attributed to the bending vibration peaks of Fe3O4; 798, 887 cm⁻¹ -1 The characteristic peaks of Fe-OH at 1010 and 1107 cm⁻¹ belong to the bending vibration peaks of α-FeOOH; -1 The characteristic peak of Fe-OH at 1421 cm⁻¹ belongs to the asymmetric stretching vibration peak of γ-FeOOH. -1 The characteristic peak of CO at 1655 cm⁻¹ belongs to the antisymmetric stretching vibration peak of the CO bond in FeCO₃; -1 The presence of a characteristic OH peak at this location indicates the presence of a certain amount of adsorbed water in the sample.

[0070] Comparison of the spectra of samples after different reinforcement treatments shows that after cyclic reinforcement treatment, the sample at 477 cm⁻¹... -1 562cm -1 798 cm -1 887 cm -1The characteristic peak intensity at 1010 cm- gradually increases with the number of reinforcement cycles, and the peak shape becomes increasingly sharp and regular. This indicates that as the cyclic reinforcement process progresses, the amount of stable iron oxides such as Fe2O3, Fe3O4, and α-FeOOH continuously increases, and the crystallization environment of the iron oxides becomes more homogeneous, with a significant increase in crystallinity. Meanwhile, the untreated original sample at 1010 cm- shows a significantly higher intensity. -1 1107 cm -1 The characteristic peak of γ-FeOOH at the location was extremely weak, but after cyclic reinforcement treatment, the characteristic peak at this location became clearly visible and the peak intensity increased slightly with the number of reinforcement cycles. This indicates that a new γ-FeOOH phase was induced during the cyclic reinforcement process and became one of the components of the rust layer.

[0071] Step 2: Preparation and use of compound alcohol hydrolysate

[0072] A compound alcohol solvent was prepared by thoroughly mixing 50 mL of ethanol, 10 mL of ethylene glycol, 10 mL of 1,2-propanediol, and 10 mL of ultrapure water. Then, 10 mL of HDTMS was added dropwise to the compound alcohol solvent, and citric acid was added to adjust the pH to 5. The mixture was stirred and hydrolyzed at 40 °C for 5 h to obtain a hydrolysate. The rusty iron pot fragment sample, which had undergone 30 cycles of soaking and drying in step 1, was completely immersed in the obtained hydrolysate. After soaking for 10 min, the sample was removed and allowed to air dry at room temperature to obtain a stabilized and protected iron artifact sample.

[0073] Depend on Figure 11 It can be observed that, compared with the original rusted iron pot fragments, after being stored in a constant temperature and humidity chamber at 25 ℃ and 80% humidity for 3 weeks, new cracks appeared on the sample surface, which continued to expand until they covered the entire sample. Subsequently, under room temperature storage conditions, the cracks gradually opened up, and even powdering occurred. After the rusted iron pot fragments were stabilized and protected, and then stored at room temperature for 30 days after being stored in a constant temperature and humidity chamber at 25 ℃ and 80% humidity for 3 weeks, the sample surface was completely covered with HDTMS and the modification was uniform. The appearance was very similar to that of the original rusted iron pot fragments, which meets the principles of cultural relic protection.

[0074] Depend on Figure 12 It is evident that the original sample of the rusty iron pot fragments had a small number of cracks on its surface. After being stored in a constant temperature and humidity chamber at 25 ℃ and 80% humidity for 3 weeks, the cracks concentrated and expanded to the millimeter level. The sample of the rusty iron pot fragments after the stabilization and protection treatment did not have obvious large cracks on its surface. After being stored in a constant temperature and humidity chamber at 25 ℃ and 80% humidity for 3 weeks, no large and deep cracks appeared on the sample surface, and HDTMS was still uniformly covered on the sample surface.

[0075] Depend on Figure 13As can be seen, when the color difference of three random points on the rusty iron pot fragment sample after the stabilization and protection treatment was compared with that of the original rusty iron pot fragment sample, and each point was taken three times, the final ΔE values ​​were 3.21, 3.48 and 2.89, respectively. The ΔE values ​​were all less than 3.5, and the difference was difficult to detect with the naked eye.

[0076] Depend on Figure 14 As can be seen, the characteristic absorption peaks in the spectrum are assigned as follows: the original sample at 477 cm⁻¹ -1 The characteristic peaks of Fe-O are attributed to the bending vibrations of Fe2O3; 562 cm⁻¹ -1 The characteristic peaks of Fe-O are attributed to the bending vibration peaks of Fe3O4; 798, 887 cm⁻¹ -1 The characteristic peak of Fe-OH at 1421 cm⁻¹ belongs to the bending vibration peak of α-FeOOH; -1 The characteristic peak of CO at this location is attributed to the antisymmetric stretching vibration peak of the CO bond in FeCO3; in the sample after reinforcement and sealing treatment, the peaks at 2925 and 2954 cm⁻¹ are... -1 Characteristic peaks of -CH3 and -CH2- appeared at 1030 cm⁻¹, and these bands are related to the presence of aliphatic chains. -1 The absorption peak intensity at the point is significantly increased, corresponding to the asymmetric stretching vibration of Si-O-Si. The surface HDTMS has been successfully grafted onto the sample surface. At the same time, the absorption peak intensities of Fe2O3, Fe3O4, and α-FeOOH are all weakened to varying degrees, indicating that HDTMS has been uniformly covered on the sample surface and has a physical shielding effect on the infrared signal of the internal iron oxide.

[0077] Further contact angle tests were conducted on the rusted iron pot fragments after the aforementioned stabilization and protection treatment. Figure 15 As can be seen, the surface contact angle of the rusty iron pot fragment sample after stabilization and protection treatment is 123°. After being completely dried at room temperature and stored in a constant temperature and humidity chamber at 25°C and 80% humidity for 4 weeks, the surface contact angle is 120°. After being stored in the constant temperature and humidity chamber at 25°C and 80% humidity for 4 weeks and then stored at room temperature for 30 days, the surface contact angle is 119°. This shows that the hydrophobicity of the rusty iron pot fragment sample after stabilization and protection treatment is not significantly reduced after storage in a high humidity environment and then at room temperature, indicating that the rusty and fragile iron artifact sample treated by the method of this invention has good anti-aging properties.

[0078] Based on the above experimental results, this invention significantly improves the structural strength of rusty and fragile iron artifacts by subjecting them to a cyclic soaking and drying process with a consolidation solution. This process fills surface pores and cracks, reduces surface roughness, and the hydrolysate of the silane coupling agent, using a solvent of ethanol, ethylene glycol, and 1,2-propanediol, forms a uniform and dense protective layer with a corrosion inhibition efficiency of 88.1%. The entire treatment process is gentle and non-destructive, resulting in minimal difference in appearance from the original. The samples exhibit excellent hydrophobicity and anti-aging properties, adhering to the principle of "restoring the old as it was, with minimal intervention" in artifact preservation. This effectively solves the problems of cracking and crumbling in the preservation of rusty and fragile iron artifacts, enhances the strength of the rust layer, and preserves the original form of the ironware.

Claims

1. A method for reinforcing and protecting rusted and fragile iron cultural relics, characterized in that... The method consists of the following steps: Step 1: Preparation and use of reinforcement fluid L-ascorbic acid was added to an aqueous citric acid solution and stirred until completely dissolved. Then, FeCO3 powder was added and stirring continued until the system turned a uniform light green color. After standing, the supernatant was collected to obtain a consolidation solution with a ferrous ion concentration of 0.1–0.4 mol / L. The rusty and fragile iron artifact was completely immersed in the above consolidation solution, ensuring that no part of the artifact was exposed to air. At the same time, the artifact was fixed with a support to prevent it from directly contacting the container wall. After soaking for 10–15 minutes, the iron artifact was removed and placed in a forced-air drying oven to dry, completing one soaking-drying treatment. The above soaking-drying treatment was repeated until the weight of the iron artifact no longer increased, resulting in a pretreated iron artifact. Step 2: Preparation and use of compound alcohol hydrolysate Ethanol, ethylene glycol, 1,2-propanediol, and ultrapure water were thoroughly mixed to prepare a compound alcohol solvent, wherein the volume ratio of ethanol, ethylene glycol, and 1,2-propanediol in the compound alcohol solvent was 3-7:1:0-1. Hexadecyltrimethoxysilane was added dropwise to the compound alcohol solvent, and citric acid was added to adjust the pH to 4-6. The mixture was stirred and hydrolyzed to obtain a hydrolysate. The pretreated iron artifact was completely immersed in the obtained hydrolysate for 10-15 minutes, then removed and allowed to air dry at room temperature to obtain a well-preserved iron artifact.

2. The method for reinforcing and protecting rusted and fragile iron cultural relics according to claim 1, characterized in that: In step 1, the concentration of citric acid in the citric acid aqueous solution is 0.1–0.2 mol / L.

3. The method for reinforcing and protecting rusted and fragile iron cultural relics according to claim 1, characterized in that: In step 1, the molar ratio of citric acid to L-ascorbic acid is 1:0.03 to 0.

05.

4. The method for reinforcing and protecting rusted and fragile iron cultural relics according to claim 1, characterized in that: In step 1, the molar ratio of FeCO3 to citric acid is 1:0.2 to 0.

5.

5. The method for reinforcing and protecting rusted and fragile iron cultural relics according to claim 1, characterized in that: In step 1, the iron artifact sample is taken out and placed in a forced-air drying oven at 20-40 ℃ for 6-10 hours.

6. The method for reinforcing and protecting rusted and fragile iron cultural relics according to claim 1, characterized in that: In step 2, the volume ratio of ethanol, ethylene glycol, and 1,2-propanediol in the compound alcohol solvent is 5:1:

1.

7. The method for reinforcing and protecting rusted and fragile iron cultural relics according to claim 1, characterized in that: In step 2, the total volume ratio of ethanol, ethylene glycol, and 1,2-propanediol to ultrapure water is 4 to 9:

1.

8. The method for reinforcing and protecting rusted and fragile iron cultural relics according to claim 1, characterized in that: In step 2, the volume ratio of hexadecyltrimethoxysilane to the compound alcohol solvent is 5 to 10:

1.

9. The method for reinforcing and protecting rusted and fragile iron cultural relics according to claim 1, characterized in that: In step 2, the mixture is stirred and hydrolyzed at 35–50 °C for 4–6 hours.

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