Stabilization Treatment Liquid for 690 Mpa-Grade Weather-Resistant Bridge Steel Member, Treatment Method and Use

The present disclosure pertains to the technical field of corrosion and protection and relates to the technology for protecting weather-resistant bridge steel members, particularly to a stabilization treatment liquid and a treatment method for 690 MPa-grade weather-resistant bridge steel members.

The use of weather-resistant bridge steel without painting enables significant reduction in painting cost, environmental protection, shortening of construction period, and great reduction in maintenance cost during operation of the bridge (a full life cycle is very advantageous in terms of cost). However, if the rust layer is not stabilized, it will generally take 3 to 10 years for the surface rust layer of the weather-resistant bridge steel to stabilize gradually. In addition, for a paint-free weather-resistant steel bridge, rusty water will flow out during formation of a protective rust layer, affecting the aesthetic and thinning the steel plate. This results in the phenomenon that rusty liquid is prone to dripping and scattering in the early stage of the use of the bare weather-resistant bridge steel, which pollutes the environment, and seriously affects the consistency of the outside color of the weather-resistant bridge steel. This has become a bottleneck that restricts the promotion and application of weather-resistant bridge steel without painting. Therefore, in order to form a stable rust layer on its surface in a short time, it is necessary to stabilize the rust layer on its surface.

In order to adapt to the development of bridge steel structures towards larger spans and higher strengths in China, the strength grade of high-strength bridge steel plates has been increased to 690 MPa. However, there is so far no technology available for stabilizing the rust layer of a high-strength weather-resistant bridge steel member. Moreover, a weather-resistant bridge steel member is formed by processing and welding a weather-resistant steel plate, and the commonly seen weather-resistant bridge steel member is nearly a cube. Due to the large size of the weather-resistant bridge steel member, it is difficult to flip the weather-resistant bridge steel member. Therefore, the rust layer stabilization treatment of the weather-resistant bridge steel member involves the top surface, bottom surface and side surface of the member. Because of the flow of the rust layer stabilization treatment liquid over various parts of the member, the rust layer on the surface of the weather-resistant bridge steel member that has experienced the rust layer stabilization treatment has a non-uniform color, and the rusty liquid flows thereon.

In the prior art, the patent to the Institute of Metal Research, Chinese Academy of Sciences, “RUST LAYER STABILIZATION TREATMENT AGENT FOR WEATHER-RESISTANT STEEL SURFACE BASED ON SILANE COUPLING AGENT, PREPARATION METHOD AND USE METHOD THEREOF” (CN202111080510.0) discloses a treatment agent comprising 1-50% silane coupling agent, 1-10% ethanol, 0.05-0.5% hydrolysis promoter, 0.5-10% rust layer stabilization promoter, and a balance of deionized water. The patent to Shougang Group, “RUST LAYER STABILIZATION TREATMENT AGENT FOR WEATHER-RESISTANT STEEL SURFACE AND COATING TREATMENT METHOD FOR WEATHER-RESISTANT STEEL SURFACE” (CN202010666089.0), discloses a film-forming agent: 50-80 parts; an inducer: 1-10 parts; a phosphating agent: 0.2-1 part; an accelerator: 1-5 parts; a modifier: 1-10 parts; a corrosion inhibitor: 1-10 parts; a surface aid: 0.05-0.3 parts; a wetting and dispersing agent: 0.05-0.4 parts; a leveling agent: 0.05-0.4 parts. The patent to Lanzhou University of Technology, “SURFACE STABILIZATION TREATMENT AGENT AND TREATMENT METHOD FOR WEATHER-RESISTANT STEEL SUITABLE FOR INDUSTRIAL ATMOSPHERIC ENVIRONMENT” (CN202110934825.0), discloses a treatment agent comprising the following raw materials: CuSO0.8-1.2%, Cr(SO)2.8-3.2%, NaHSO0.5-0.7%, FeO0.08-0.12%, and a balance of deionized water. The patent to ANSTEEL, “TREATMENT AGENT FOR RAPID GENERATION OF STABILIZED RUST LAYER ON WEATHER-RESISTANT STEEL SURFACE AND USE METHOD” (CN201710068872.5), discloses a treatment agent consisting of two parts, agent A and agent B, wherein agent A comprises by mass percentage: CuSO0.4%- 2%, NaCl 0.1%- 2.5%, FeCl0.5%- 3%, HCl 0.1%- 0.5%, and a balance of water; and agent B is an aqueous solution of a humectant, comprising 0.2% ˜3.5% of the humectant by mass percentage and a balance of water, wherein the humectant is one or more of NaHPO, NaPO, (NaPO), CHNaO·2HO.

The above-mentioned prior art documents mainly describe the stabilization treatment of the rust layer of weather-resistant steel, and no stabilization treatment liquid or treatment method involving 690 MPa-grade weather-resistant steel bridge members was found. The above patent applications all involve treatment liquids and methods for stabilization of the rust layer on the surface of weather-resistant steel, but do not involve stabilization treatment of the rust layer of a weather-resistant steel member. Moreover, the above technologies do not meet the requirements of stabilization treatment of the rust layer of high-strength (690 MPa) weather-resistant bridge steel according to the present disclosure.

Therefore, in order to overcome the shortcomings of the above-mentioned technologies, address the challenge of stabilizing the rust layer of a 690 MPa-grade weather-resistant bridge steel member, and solve the problems of non-uniform rust layer color and rusty liquid flowing on the surface, the present disclosure provides a treatment liquid for stabilizing the rust layer of a 690 MPa-grade high-strength weather-resistant bridge steel member. Another technical problem to be solved by the present disclosure is to provide a treatment method for stabilizing the rust layer of a 690 MPa-grade high-strength weather-resistant bridge steel member using the treatment liquid. Still another technical problem to be solved by the present disclosure is to provide use of the treatment liquid. In the present disclosure, 690 MPa grade means that the steel has a yield strength of ≥690 MPa.

The technical solution of the present disclosure is a stabilization treatment liquid for a 690 MPa-grade weather-resistant bridge steel member,

2-5% sodium carboxymethyl cellulose; and

The functions of the components in the stabilization treatment liquid for a 690 MPa-grade weather-resistant bridge steel member according to the present disclosure are as follows:

Ferric chloride and sodium bisulfite are used in the treatment liquid of the present disclosure as a corrodent. The oxidizing property of ferric ions and the corroding property of chloride ions and bisulfite ions are utilized to corrode and rust the 690 MPa-grade weather-resistant bridge steel member, thereby converting the elemental iron in the member into iron oxides. Chromium sulfate and potassium permanganate are used as a rust layer stabilizer. Potassium permanganate is strongly oxidative, used together with the chromium element to promote transformation of lepidocrocite and tetragonal lepidocrocite in the rust layer to goethite. The chromium element can also replace goethite to form the final stabilized rust layer in the 690 MPa-grade weather-resistant bridge steel member. Polypropylene glycol is used as a humectant, which, by means of its low volatility, maintains the moisture of the treatment liquid and prolongs the reaction time of the effective reaction components in the treatment liquid. Sodium carboxymethyl cellulose is used as a thickener, and the thickener component in the treatment liquid is fully hydrated to form a macromolecular substance, thereby reducing the flowability of the treatment liquid and increasing the residence time of the treatment liquid on the side surface or inclined surface of the member. The addition of sodium carboxymethyl cellulose according to the present disclosure increases the residence time by 3 to 5 times than no addition of sodium carboxymethyl cellulose.

The corrodent and the rust layer stabilizer in the treatment liquid of the present disclosure promote the formation of a stable rust layer on the 690 MPa-grade weather-resistant bridge steel member. The addition of the humectant and the thickener increases the electrochemical and chemical reaction time with the surface of the member. The four components work synergistically to ensure that a brown rust layer with uniform color and no rusty liquid flowing is formed on the surface of the 690 MPa-grade weather-resistant bridge steel member.

In one or more embodiments, the mass percentage of ferric chloride in the stabilization treatment liquid for a 690 MPa-grade weather-resistant bridge steel member according to the present disclosure is 3-7%, for example, 3%, 4%, 4.5%, 5%, 6%, 7%.

In one or more embodiments, the mass percentage of sodium bisulfite in the stabilization treatment liquid for a 690 MPa-grade weather-resistant bridge steel member according to the present disclosure is 1-2%, for example, 1%, 1.2%, 1.5%, 1.6%, 1.9%, 2%.

In one or more embodiments, the mass percentage of chromium sulfate in the stabilization treatment liquid for a 690 MPa-grade weather-resistant bridge steel member according to the present disclosure is 3-6%, for example, 3%, 4%, 4.5%, 5%, 5.5%, 6%.

In one or more embodiments, the mass percentage of potassium permanganate in the stabilization treatment liquid for a 690 MPa-grade weather-resistant bridge steel member according to the present disclosure is 1-4%, for example, 1%, 2%, 2.5%, 3%, 3.5%, 4%.

In one or more embodiments, the mass percentage of polypropylene glycol in the stabilization treatment liquid for a 690 MPa-grade weather-resistant bridge steel member according to the present disclosure is 1-2%, for example, 1%, 1.2%, 1.5%, 1.7%, 1.8%, 2%.

In one or more embodiments, the mass percentage of sodium carboxymethyl cellulose in the stabilization treatment liquid for a 690 MPa-grade weather-resistant bridge steel member according to the present disclosure is 2-5%, for example, 2%, 3%, 3.5%, 3.8%, 4%, 5%.

In one or more embodiments, in the stabilization treatment liquid for a 690 MPa-grade weather-resistant bridge steel member according to the present disclosure, the mass percentage contents of the components are: 4-5% ferric chloride; 1-2% sodium bisulfite; 4-5% chromium sulfate; 2-3% potassium permanganate; 1-2% polypropylene glycol; 2-4% sodium carboxymethyl cellulose; and a balance of deionized water.

In the stabilization treatment liquid for a 690 MPa-grade weather-resistant bridge steel member according to the present disclosure, preferably, the mass percentage contents of the components in the stabilization treatment liquid are: 4-5% ferric chloride; 1-1.5% sodium bisulfite; 4-5% chromium sulfate; 2-3% potassium permanganate; 1-1.5% polypropylene glycol; 2-3% sodium carboxymethyl cellulose; and a balance of deionized water.

The present disclosure further provides a method for treating a 690 MPa-grade weather-resistant bridge steel member with a stabilization treatment liquid, or a method for stabilization treatment of a 690 MPa-grade weather-resistant bridge steel member, comprising the following steps:

A brown rust layer with uniform color and no rusty liquid flowing is formed on the surface of the 690 MPa-grade weather-resistant bridge steel member obtained according to the method of the present disclosure.

In the present disclosure, the standard of Sa2 grade follows Article 3.2.3 of National Standard of the People's Republic of China GB 8923-88 “Rust grades and preparation grades of steel surfaces before application of paints and related products”.

The principle of the method for stabilization treatment of a 690 MPa-grade weather-resistant bridge steel member according to the present disclosure is as follows:

During the formulation of the treatment liquid, an agitator is used for the agitation to mix the components evenly on the one hand, and on the other hand, to fully hydrate the thickener component in the treatment liquid to form a macromolecular substance, thereby increasing the viscosity of the treatment liquid.

By sandblasting the surface of the 690 MPa-grade weather-resistant bridge steel member, the iron oxide scale on the surface of the member can be removed, and the surface roughness can be increased. As a result, the amount of the treatment liquid adhered to the member surface and the reaction time can be increased, thereby improving the effect in stabilizing the rust layer.

Because the amount of the treatment liquid adhered to the member surface has a direct influence on the color of the rust layer on the treated surface, uniform spraying must be ensured during the treatment process, and the accumulated liquid present on the top and bottom surfaces and other parts of the member must be eliminated. This ensures that the surface color of the treated member is uniform. Preferably, the amount of the treatment liquid used is ensured to be 1-2 L/m.

Drying in flowing air increases the oxygen content in the treatment liquid, thereby promoting the chemical and electrochemical reactions in the stabilization treatment.

In the method for treating a 690 MPa-grade weather-resistant bridge steel member with a stabilization treatment liquid or the method for stabilization treatment of a 690 MPa-grade weather-resistant bridge steel member according to the present disclosure, preferably, the agitation in step (1) is performed using an agitator; and the agitating speed is preferably set to 300-500 rpm, for example, 300 rpm, 350 rpm, 400 rpm, 440 rpm, 500 rpm.

Further, the agitating time of the treatment liquid in step (1) is 1-2 hours, for example, 1 hour, 1.2 hours, 1.5 hours, 1.6 hours, 1.8 hours, 2 hours.

Preferably, the amount of the treatment liquid used in step (3) is 1-2 L/m, for example, 1 L/m, 1.2 L/m, 1.5 L/m, 1.8 L/m, 2 L/m.

In the method for treating a 690 MPa-grade weather-resistant bridge steel member with a stabilization treatment liquid or the method for stabilization treatment of a 690 MPa-grade weather-resistant bridge steel member according to the present disclosure, preferably, the accumulated liquid is removed using a roller brush in step (4).

In the method for treating a 690 MPa-grade weather-resistant bridge steel member with a stabilization treatment liquid or the method for stabilization treatment of a 690 MPa-grade weather-resistant bridge steel member according to the present disclosure, preferably, the time for drying in flowing air is ≥15 days, for example, 15 days, 2 days, 25 days, 28 days, 29 days, or 30 days.

In the method for treating a 690 MPa-grade weather-resistant bridge steel member with a stabilization treatment liquid or the method for stabilization treatment of a 690 MPa-grade weather-resistant bridge steel member according to the present disclosure, preferably, the drying in flowing air is carried out outdoors in step (5).

By placing the member outdoors, under the influence of rain, dew and sunlight, dry and wet environments are generated alternately on the member surface, which accelerates the formation of the stable rust layer on the member surface.

More preferably, the time for drying in flowing air is 15-30 days. The longer the time for drying in flowing air, the more stable the rust layer of the member.

The stable rust layer obtained by using the stabilization treatment liquid and treatment method for a 690 MPa-grade weather-resistant bridge steel member according to the present disclosure has the following technical parameters: (1) a thickness of the rust layer on the member surface >80 μm, for example, 85 μm, 88 μm, 90 μm, 92 μm, 95 μm; (2) a color difference value λE of the rust layer on the surface at different locations of the member ≤10, for example, 4, 4.5, 5, 6, 7, 9; (3) an amount of the rust layer on the member surface ≥25 g/m, for example, 28 g/m, 29 g/m, 30 g/m, 32 g/m, 35 g/m.

The technical parameters of natural rusting of a 690 MPa-grade weather-resistant bridge steel member: (1) a thickness of the rust layer on the member surface: 10-40 μm; (2) a color difference value λE of the rust layer on the surface at different locations of the member: 20-50; (3) an amount of the rust layer on the member surface: 5-10 g/m.

The present disclosure further provides use of the above-mentioned stabilization treatment liquid in the stabilization treatment of a 690 MPa-grade weather-resistant bridge steel member.

By comparing the present disclosure with the prior art,

To better explain the present disclosure, the stabilization treatment liquid and treatment method for a 690 MPa-grade weather-resistant bridge steel member will be described in detail below with reference to the specific Examples.

The parameters in the Examples were tested according to the following methods:

Measurement of the rust layer thickness: A coating thickness gauge was used to measure the rust layer thickness of a weather-resistant bridge steel member. An area of less than 0.01 mwas selected from the part to be tested, 10 points were selected in this area to measure the rust layer thickness, and the average rust layer thickness of the test points was calculated.

Measurement of the color difference value λE of the rust layer on the surface at different locations of a member: A colorimeter was used to detect the color uniformity of the rust layer of a weather-resistant bridge steel member. The rust layer at a point of the part to be tested was selected as a standard sample. The color difference values AEs of the rust layer at 10 points of the member were measured. The average color difference value λE of the test points was calculated.

Measurement of the amount of the rust layer on the surface of a member: A weight loss method was used to measure the amount of the rust layer on the surface of a member. When processing a member, 3-5 test pieces were processed simultaneously. The length, width, height and weight W1 of a test piece were measured, and the surface area S was calculated. The test piece was pickled to remove the rust, and the weight W2 after pickling was weighed.

The amount of the rust layer on the surface of a member=(W1−W2)/S.

A stabilization treatment liquid for a 690 MPa-grade weather-resistant bridge steel member was formulated based on mass percentage. The components were weighed according to the following mass percentage contents: 3% ferric chloride, 1% sodium bisulfite, 3% chromium sulfate, 1% potassium permanganate, 1% polypropylene glycol, 2% sodium carboxymethyl cellulose, and a balance of deionized water. The treatment liquid was agitated for 1 hour using an agitator set at an agitating speed of 300 rpm. The surface of the weather-resistant bridge steel member was sandblasted to a surface grade of Sa2. A spraying device was used to evenly spray the treatment liquid onto the side surface, top surface, bottom surface and other parts of the member. The amount of the treatment liquid used was 1.8 L/m. A roller brush was used to remove the accumulated liquid present on the top surface, bottom surface and other parts. The member was placed outdoors for 15 days to dry in flowing air. After the treatment, a brown rust layer with uniform color and no rusty liquid flowing was formed on the surface of the 690 MPa-grade weather-resistant bridge steel member. The thickness of the rust layer on the surface of the member was 85 μm, the color difference value λE of the rust layer on the surface at different locations of the member was 9, and the amount of the rust layer on the surface of the member was 28 g/m.

A stabilization treatment liquid for a 690 MPa-grade weather-resistant bridge steel member was formulated based on mass percentage. The components were weighed according to the following mass percentage contents: 4% ferric chloride, 1.5% sodium bisulfite, 4% chromium sulfate, 2% potassium permanganate, 2% polypropylene glycol, 3% sodium carboxymethyl cellulose, and a balance of deionized water. The treatment liquid was agitated for 2 hours using an agitator set at an agitating speed of 400 rpm. The surface of the weather-resistant bridge steel member was sandblasted to a surface grade of Sa2. A spraying device was used to evenly spray the treatment liquid onto the side surface, top surface, bottom surface and other parts of the member. The amount of the treatment liquid used was 1.5 L/m. A roller brush was used to remove the accumulated liquid present on the top surface, bottom surface and other parts. The member was placed outdoors for 30 days to dry in flowing air. After the treatment, a brown rust layer with uniform color and no rusty liquid flowing was formed on the surface of the 690 MPa-grade weather-resistant bridge steel member. The thickness of the rust layer on the surface of the member was 90 μm, the color difference value λE of the rust layer on the surface at different locations of the member was 5, and the amount of the rust layer on the surface of the member was 30 g/m.

A stabilization treatment liquid for a 690 MPa-grade weather-resistant bridge steel member was formulated based on mass percentage. The components were weighed according to the following mass percentage contents: 7% ferric chloride, 2% sodium bisulfite, 6% chromium sulfate, 4% potassium permanganate, 2% polypropylene glycol, 5% sodium carboxymethyl cellulose, and a balance of deionized water. The treatment liquid was agitated for 2 hours using an agitator set at an agitating speed of 500 rpm. The surface of the weather-resistant bridge steel member was sandblasted to a surface grade of Sa2. A spraying device was used to evenly spray the treatment liquid onto the side surface, top surface, bottom surface and other parts of the member. The amount of the treatment liquid used was 1 L/m. A roller brush was used to remove the accumulated liquid present on the top surface, bottom surface and other parts. The member was placed outdoors for 28 days to dry in flowing air. After the treatment, a brown rust layer with uniform color and no rusty liquid flowing was formed on the surface of the 690 MPa-grade weather-resistant bridge steel member. The thickness of the rust layer on the surface of the member was 88 um, the color difference value λE of the rust layer on the surface at different locations of the member was 6, and the amount of the rust layer on the surface of the member was 32 g/m.

A stabilization treatment liquid for a 690 MPa-grade weather-resistant bridge steel member was formulated based on mass percentage. The components were weighed according to the following mass percentage contents: 6% ferric chloride, 1.6% sodium bisulfite, 5.5% chromium sulfate, 3.5% potassium permanganate, 1.5% polypropylene glycol, 3.5% sodium carboxymethyl cellulose, and a balance of deionized water. The treatment liquid was agitated for 1.5 hours using an agitator set at an agitating speed of 350 rpm. The surface of the weather-resistant bridge steel member was sandblasted to a surface grade of Sa2. A spraying device was used to evenly spray the treatment liquid onto the side surface, top surface, bottom surface and other parts of the member. The amount of the treatment liquid used was 1.2 L/m. A roller brush was used to remove the accumulated liquid present on the top surface, bottom surface and other parts. The member was placed outdoors for 25 days to dry in flowing air. After the treatment, a brown rust layer with uniform color and no rusty liquid flowing was formed on the surface of the 690 MPa-grade weather-resistant bridge steel member. The thickness of the rust layer on the surface of the member was 88 μm, the color difference value λE of the rust layer on the surface at different locations of the member was 7, and the amount of the rust layer on the surface of the member was 29 g/m.

A stabilization treatment liquid for a 690 MPa-grade weather-resistant bridge steel member was formulated based on mass percentage. The components were weighed according to the following mass percentage contents: 4.5% ferric chloride, 1.9% sodium bisulfite, 4.5% chromium sulfate, 2.5% potassium permanganate, 1.7% polypropylene glycol, 3.8% sodium carboxymethyl cellulose, and a balance of deionized water. The treatment liquid was agitated for 1.6 hours using an agitator set at an agitating speed of 440 rpm. The surface of the weather-resistant bridge steel member was sandblasted to a surface grade of Sa2. A spraying device was used to evenly spray the treatment liquid onto the side surface, top surface, bottom surface and other parts of the member. The amount of the treatment liquid used was 2 L/m. A roller brush was used to remove the accumulated liquid present on the top surface, bottom surface and other parts. The member was placed outdoors for 29 days to dry in flowing air. After the treatment, a brown rust layer with uniform color and no rusty liquid flowing was formed on the surface of the 690 MPa-grade weather-resistant bridge steel member. The thickness of the rust layer on the surface of the member was 92 μm, the color difference value λE of the rust layer on the surface at different locations of the member was 4.5, and the amount of the rust layer on the surface of the member was 27 g/m.