阅读说明：本技术 一种解决海洋工程用合金钢紧固件锈蚀锈死及断裂的方法 (Method for solving corrosion, rust and breakage of alloy steel fastener for ocean engineering ) 是由 陈继志 孙永伟 范芳雄 王灵水 于 2020-04-21 设计创作，主要内容包括：一种解决海洋工程用合金钢紧固件锈蚀锈死及断裂的方法,利用延伸率≥8%的一层阴极性镀层或复合阴极性镀层对清洁后的合金钢紧固件的表面进行包覆处理,形成阴极性柔性阻氢镀层。依靠镀层自身的高耐蚀性,能够有效解决合金钢紧固件的锈蚀、锈死及断裂问题,避免阳极性镀层溶解过程中产生的析氢现象,且其致密性结构能够阻挡氢原子渗透基体。电镀阴极性镍基合金镀层,如Ni、Ni-W、Ni-P、Ni-Co、Ni-Cr、Ni-W-P、Ni-Cr-W镀层等,制备及使用过程中环保、无污染,性价比高,具有很大的工程应用价值。(A method for solving corrosion, rust and fracture of an alloy steel fastener for ocean engineering is characterized in that a layer of cathodic coating or composite cathodic coating with the elongation rate of more than or equal to 8% is used for coating the surface of the cleaned alloy steel fastener to form a cathodic flexible hydrogen-resistant coating. By means of the high corrosion resistance of the plating layer, the problems of corrosion, rust and breakage of the alloy steel fastener can be effectively solved, the hydrogen evolution phenomenon generated in the dissolving process of the anodic plating layer is avoided, and the compact structure can prevent hydrogen atoms from permeating into the matrix. Electroplating a cathodic nickel-based alloy plating layer, such as Ni, Ni-W, Ni-P, Ni-Co, Ni-Cr, Ni-W-P, Ni-Cr-W plating layer and the like, and has the advantages of environmental protection, no pollution, high cost performance and great engineering application value in the preparation and use processes.)

1. A method for solving corrosion, rust and breakage of an alloy steel fastener for ocean engineering is characterized by comprising the following steps: and coating the surface of the cleaned alloy steel fastener by using a layer of cathodic coating or composite cathodic coating with the elongation rate of more than or equal to 8% to form a cathodic flexible hydrogen-resistant coating.

2. The method for solving the problems of rust, rust and cracking of the alloy steel fastener for ocean engineering as claimed in claim 1, wherein: the composite cathode coating is formed by at least two layers of cathode coatings which are coated with alloy steel fasteners layer by layer and then are compounded after being dried.

3. The method for solving the problems of rust, rust and cracking of the alloy steel fastener for ocean engineering as claimed in claim 1, wherein: before the surface of the alloy steel fastener is subjected to cladding treatment, a layer of Ni is pre-plated on the surface of the alloy steel fastener.

4. The method for solving the problems of rust, rust and cracking of the alloy steel fastener for ocean engineering as claimed in claim 1, wherein: and coating the surface of the alloy steel fastener in an electroplating mode to enable the cathode plating layer to form a nanocrystalline structure.

5. The method for solving the problem of rust, rust and breakage of the alloy steel fastener for ocean engineering as claimed in claim 1 or 2, wherein: the cathode coating is one of Ni coating, Ni-W coating, Ni-P coating, Ni-Co coating, Ni-Cr coating, Ni-W-P coating and Ni-Cr-W coating.

Technical Field

The invention relates to the technical field of ocean engineering, in particular to a method for solving corrosion, rust and breakage of an alloy steel fastener for ocean engineering.

Background

The fastener is used as a connecting part, is widely applied to ships and ocean engineering equipment and faces the complex severe environment of ocean atmosphere and seawater medium. In the ship construction process, the alloy steel fastener is often rusted and rusted, so that the delivery and use are seriously influenced; in addition, with alloy steel fastener strength rating (tensile strength)R _mGreater than 1000MPa), increased hydrogen induced fracture sensitivity, and influence by marine atmosphere and seawater medium environment, leading to plastic loss of fastener material, even unexpected delayed fracture, and causing damage to the safe operation of equipment. The phenomena of failure and fault of alloy steel fasteners for ships and ocean engineering are widely concerned and paid attention by people, but the problems are not substantially solved.

The surface of an alloy steel fastener for ships and ocean engineering is plated with an anodic coating with better corrosion resistance such as Zn, Zn-Al, Zn-Ni, Cd-Ti and the like, and after the alloy steel fastener is in service in a marine environment for a certain time, the low-strength fastener is often rusted and rusted, and the high-strength fastener is often subjected to hydrogen induced fracture. The essential reasons for this problem are: on one hand, the anodic coating is quickly dissolved by the coating, so that the matrix is protected from corrosion, and the fastener is corroded and rusted after the anodic coating is quickly dissolved; on the other hand, for the high-strength fastener, due to galvanic corrosion, crevice corrosion, external potential protection and anodic coating dissolution caused by a connecting structure, an electrochemical reaction mechanism exists, namely, the anodic dissolution and cathodic hydrogen evolution are in a conjugation process, particularly, the anodic coating generates hydrogen evolution in the electrochemical corrosion process, generated hydrogen atoms permeate into a fastener matrix, are adsorbed, aggregated and diffused in a stress concentration area at the root of a thread or at the hexagonal head/rod part, so that the bonding force at a local grain boundary is reduced, hydrogen-induced microcracks are formed, and when the hydrogen content reaches a certain critical value along with the continuous aggregation of the hydrogen atoms, the high-strength fastener is subjected to delayed fracture.

The current research mainly focuses on an anode plating layer protection method with good corrosion resistance, and based on the marine environment, the corrosion and hydrogen evolution of a connection structure caused by galvanic corrosion, crevice corrosion, additional cathodic protection and anode plating layer dissolution cause plating layer failure or material deterioration.

Disclosure of Invention

In order to solve the technical problems, the invention provides a method for solving the problems of corrosion, rust and fracture of an alloy steel fastener for ocean engineering.

In order to realize the technical purpose, the adopted technical scheme is as follows: a method for solving corrosion, rust and fracture of an alloy steel fastener for ocean engineering is characterized in that a layer of cathodic coating or composite cathodic coating with the elongation rate of more than or equal to 8% is used for coating the surface of the cleaned alloy steel fastener to form a cathodic flexible hydrogen-resistant coating.

The composite cathode coating is formed by at least two layers of cathode coatings which are coated with alloy steel fasteners layer by layer and then are compounded after being dried.

Before the surface of the alloy steel fastener is subjected to cladding treatment, a layer of Ni is pre-plated on the surface of the alloy steel fastener.

And coating the surface of the alloy steel fastener in an electroplating mode to enable the cathode plating layer to form a nanocrystalline structure.

The cathode coating is one of Ni coating, Ni-W coating, Ni-P coating, Ni-Co coating, Ni-Cr coating, Ni-W-P coating and Ni-Cr-W coating.

The invention has the beneficial effects that: the cathodic flexible hydrogen-resistant coating is electroplated on the surface of the alloy steel fastener, the corrosion and rust problems of the alloy steel fastener can be effectively solved by virtue of the high corrosion resistance of the coating, the hydrogen evolution phenomenon generated in the dissolution process of the anodic coating is avoided, and the compact structure of the coating can prevent hydrogen atoms from permeating a matrix. Electroplating a cathodic nickel-based alloy plating layer, such as Ni, Ni-W, Ni-P, Ni-Co, Ni-Cr, Ni-W-P, Ni-Cr-W plating layer and the like, and has the advantages of environmental protection, no pollution, high cost performance and great engineering application value in the preparation and use processes.

Drawings

FIG. 1 is a surface corrosion topography of a low strength (8.8 grade) physical pre-tensioned fastener (40Cr) under different plating protections after 12 days of peri-immersion corrosion;

FIG. 2 is a comparison graph of the low strength (grade 8.8) non-plated pre-tightened fastener (40Cr) corrosion morphology-1 # specimen after 30 days of weekly immersion corrosion;

FIG. 3 is a comparison of low strength (grade 8.8) pre-tightened fastener (40Cr) with Dacromet plating corrosion profile-1 # specimens after 30 days of immersion corrosion;

FIG. 4 is a comparison graph of the low strength (grade 8.8) non-plated pre-tightened fastener (40Cr) corrosion profile-2 # specimens after 30 days of weekly immersion corrosion;

FIG. 5 is a graph of the erosion profile-2 # specimen of a low strength (grade 8.8) pre-tensioned fastener (40Cr) with Dacromet plating after 30 days of weekly immersion erosion;

FIG. 6 is a corrosion profile after unloading of the low strength (grade 8.8) fastener (40Cr) + Ni-W-P plating after 30 days of weekly immersion corrosion;

FIG. 7 is a detail drawing of the A section of the thread of the low strength (grade 8.8) fastener (40Cr) + Ni-W-P coating of FIG. 6 after unloading;

FIG. 8 is a detail drawing of the A section of the thread of the low strength (grade 8.8) fastener (40Cr) + Ni-W-P coating of FIG. 6 after unloading;

FIG. 9 is a detail drawing of the A section of the thread of the low strength (grade 8.8) fastener (40Cr) + Ni-W-P coating of FIG. 6 after unloading;

FIG. 10 is a detail view of the B-section thread of the low strength (grade 8.8) fastener (40Cr) + Ni-W-P coating of FIG. 6 after unloading;

FIG. 11 is a detail view of the B-section thread of the low strength (grade 8.8) fastener (40Cr) + Ni-W-P coating of FIG. 6 after unloading;

FIG. 12 is a macro topography of a high strength (10.9 grade) 42CrMo + Cd-Ti plated fastener after 90 days of immersion corrosion;

FIG. 13 is a macroscopic view of a high strength (10.9 grade) 42CrMo steel + Ni-W-P plated fastener after 90 days of immersion corrosion;

FIG. 14 shows the fatigue frequency of 0 and 5 × 10⁵Second, 1.5 × 10⁶Second, 2.0 × 10⁶A strain amount measurement chart for the flexibility evaluation of the Ni-W-P plating layer under the condition;

FIG. 15 is a graph showing the change of hydrogen content in steel matrix after different coatings are charged with hydrogen.

Detailed Description

A method for solving corrosion, rust and fracture of an alloy steel fastener for ocean engineering is characterized in that a layer of cathodic coating or composite cathodic coating with the elongation rate of more than or equal to 8% is used for coating the surface of the cleaned alloy steel fastener to form a cathodic flexible hydrogen-resistant coating. The cathode coating can reduce or avoid the problems of rapid loss and hydrogen evolution caused by coating dissolution; meanwhile, the dynamic strain and concentration of the working state of the gap area of the fastener are considered, and a flexible coating of the cathodic coating with the elongation rate of more than or equal to 8 percent is selected; in order to effectively solve the hydrogen infiltration risk caused by cathodic protection, galvanic corrosion, crevice corrosion and the like, a compact hydrogen-resistant coating with low defect rate is designed. Thereby improving the damage resistance and hydrogen resistance efficiency of the plating layer and solving the problems of corrosion, rust and fracture of the fastener for ship and ocean engineering.

The negative polarity means that the self-corrosion potential of the coating under the seawater environment is negative compared with that of the fastener substrate, and the fastener substrate is an anode in the electrochemical reaction process.

The flexibility refers to the local stress and strain concentration position, the coating has certain ductility and can follow the fastener base body to generate plastic deformation without falling off or damage, and the coating has the anti-damage performance to the dynamic strain under the action of fatigue load.

The hydrogen resistance means that external hydrogen atoms can be effectively prevented from permeating into the fastener matrix, and the hydrogen resistance has certain hydrogen resistance.

The composite cathode coating is formed by at least two layers of cathode coatings which are coated with alloy steel fasteners layer by layer and then are compounded after being dried. Firstly plating a cathodic coating with the elongation rate of more than or equal to 8 percent on the surface of the alloy steel fastener, and then plating a cathodic coating with the elongation rate of more than or equal to 8 percent to complete coating compounding.

Before the surface of the alloy steel fastener is subjected to coating treatment, a layer of Ni is pre-plated on the surface of the alloy steel fastener, so that the bonding strength of the plating layer and the fastener is increased, and the alloy steel fastener is not easy to delaminate and crack.

The surface of the alloy steel fastener is coated in an electroplating mode, so that the cathode plating layer forms a nanocrystalline structure and has better corrosion resistance.

The cathode coating is one of Ni coating, Ni-W coating, Ni-P coating, Ni-Co coating, Ni-Cr coating, Ni-W-P coating and Ni-Cr-W coating.

The technical scheme of the invention is explained in detail in the following with the accompanying drawings.

A method for solving corrosion, rust and breakage of an alloy steel fastener for ocean engineering adopts a cathodic flexible hydrogen-resistant Ni-W-P plating layer as an example. The chemical components (wt%) of the Ni-W-P alloy plating layer are Ni50-90%, W5-35%, P2-15%, and the Ni-W-P alloy plating layer has a nanocrystalline structure and a thickness of 10-50 mu m. For alloy steel fasteners (the self-corrosion potential is about-650 mV vs. SCE, seawater medium), the electrochemical characteristics (the self-corrosion potential of the Ni-W-P coating is about-400 mV vs. SCE, seawater medium) are negative polarity; the nanocrystalline structure ensures good corrosion resistance, high density and excellent hydrogen resistance of the plating layer; the plating layer is plated with Ni firstly and then plated with Ni-W-P alloy, so that the plating layer has good flexibility, high bonding strength and difficult delamination and cracking. Therefore, the invention takes the anodic plating layer-Dacromet, Cd-Ti, etc. which are widely applied in the current engineering as the comparison case to explain the cathodic Ni-W-P plating layer of the invention in detail.

The method for solving the problems of rust, rust and breakage of the alloy steel fastener for ocean engineering can be obtained by the following process method:

workpiece oil removal → water cleaning → rust removal → water cleaning → electrochemical oil removal → hot water cleaning → surface activation → water cleaning → pre-plating Ni (thickness control) → plating Ni-W-P → water cleaning → hot water cleaning.

The thickness of the priming pre-electroplated Ni layer influences the flexibility of the plating layer, and the corrosion resistance, flexibility and hydrogen resistance of the Ni-W-P plating layer are comprehensively considered, so that the thickness of the priming Ni layer needs to be controlled within a certain range.