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CN-121976200-A - Compound water-based working solution for cleaning and passivating inner wall of stainless steel pipeline and application method thereof

CN121976200ACN 121976200 ACN121976200 ACN 121976200ACN-121976200-A

Abstract

The invention discloses a compound water-based working solution for cleaning and passivating the inner wall of a stainless steel pipeline and a use method thereof, the working solution is prepared by compounding an organic acid complexing agent, a fluorine-containing inorganic acid dissolvent, an oxidizing inorganic acid passivating agent, a nitrogen-containing heterocyclic metal corrosion inhibitor, an anionic surfactant and water. The application method comprises the steps of carrying out alkaline pretreatment and flushing on a stainless steel pipeline system, pumping preheated working fluid into the system for cyclic cleaning and passivation, and finally carrying out neutralization and final flushing. The invention integrates strong rust removal and high-quality passivation into one step through the synergistic effect of the components, can thoroughly remove three types of intractable red rust, effectively protect the stainless steel substrate from being corroded, keep the original silvery white luster and smoothness of the treated surface, form a compact passivation film, ensure quick recovery of the system water quality, and is suitable for regeneration maintenance of an old purified water system.

Inventors

  • LIANG DONG
  • WU RUILI

Assignees

  • 广东中安博德工程有限公司

Dates

Publication Date
20260505
Application Date
20260209

Claims (10)

  1. 1. The compound water-based working solution for cleaning and passivating the inner wall of the stainless steel pipeline is characterized by being prepared by compounding the following components: a) An organic acid complexing agent; b) A fluorine-containing inorganic acid dissolvent; c) An oxidizing inorganic acid passivating agent; d) Nitrogenous heterocyclic metal corrosion inhibitors; e) An anionic surfactant; the balance of water; The components cooperate with each other, so that the working solution can form a passivation film in situ and keep the original color of the metal substrate while the intractable red rust on the inner wall of the stainless steel pipeline is removed in the cyclic cleaning process.
  2. 2. The compound water-based working solution for cleaning and passivating the inner wall of a stainless steel pipeline according to claim 1, wherein the compound water-based working solution comprises the following components in percentage by volume: the organic acid complexing agent is 6-10%; The fluorine-containing inorganic acid dissolvent is 1-2.5%; the oxidizing inorganic acid passivating agent is 2-4%; the nitrogen-containing heterocyclic metal corrosion inhibitor is 0.1-0.5%; The anionic surfactant is 0.05-0.2%.
  3. 3. The compound water-based working fluid for cleaning and passivating the inner wall of a stainless steel pipeline according to claim 1 or 2, wherein the organic acid complexing agent is citric acid.
  4. 4. The compound water-based working fluid for cleaning and passivating the inner wall of a stainless steel pipeline according to claim 1 or 2, wherein the fluorine-containing inorganic acid dissolver is hydrofluoric acid.
  5. 5. The compound water-based working fluid for cleaning and passivating the inner wall of a stainless steel pipeline according to claim 1 or 2, wherein the oxidizing inorganic acid passivating agent is nitric acid.
  6. 6. The compound water-based working fluid for cleaning and passivating the inner wall of a stainless steel pipeline according to claim 1or2, wherein the nitrogen-containing heterocyclic metal corrosion inhibitor is benzotriazole.
  7. 7. The compound water-based working fluid for cleaning and passivating the inner wall of a stainless steel pipeline according to claim 1 or 2, wherein the anionic surfactant is sodium dodecyl benzene sulfonate.
  8. 8. The method for cleaning and passivating the intractable red rust on the inner wall of the stainless steel pipeline is characterized by at least comprising the following steps: S1, pretreatment and flushing; s2, pumping the compound water-based working solution which is preheated to 45-60 ℃ and is used for cleaning and passivating the inner wall of the stainless steel pipeline into a stainless steel pipeline system to be treated for closed cycle cleaning, wherein the cycle time is 120-240 minutes, and the flow rate during the cycle cleaning is controlled to be 0.6-1.0 m/S; S3, post-treatment and flushing.
  9. 9. The method for cleaning and passivating the intrinsic color of the refractory red rust on the inner wall of a stainless steel pipeline according to claim 8, wherein in the step S1, the pretreatment and the flushing comprise the following steps sequentially performed: S11, system evaluation and pre-flushing, namely, after the red rust grade of the wall of the stainless steel pipeline system to be treated is confirmed, emptying and high-flow flushing are carried out; S12, alkaline cleaning, namely circularly cleaning by using a weak alkaline cleaning liquid, and then flushing until the pH value of the effluent is neutral; And S13, neutralizing, softening and physically washing in an auxiliary way, namely, circularly treating by using a weakly alkaline neutralizer solution, and then physically washing in an auxiliary way and washing again until the effluent is clear.
  10. 10. The method for cleaning and passivating the intrinsic color of the refractory red rust on the inner wall of a stainless steel pipeline according to claim 8, wherein in the step S3, the post-treatment and the flushing comprise the following steps sequentially performed: S31, after the compound water-based working solution is emptied, firstly performing circulating neutralization treatment by using an alkaline neutralization solution; S32, washing the system by using purified water or water for injection with the temperature not lower than 70 ℃ until the conductivity of water at the outlet of the system is lower than 1.0 mu S/cm.

Description

Compound water-based working solution for cleaning and passivating inner wall of stainless steel pipeline and application method thereof Technical Field The invention relates to the technical field of industrial cleaning and metal surface treatment, in particular to a compound water-based working solution for cleaning and passivating the inner wall of a stainless steel pipeline and a use method thereof. Background In the industry where high purity water is critical, such as in pharmaceutical, bioengineering, microelectronics, etc., 316L stainless steel is widely used for pipes, tanks, and components of purified water storage and dispensing systems (PWSD) due to its excellent corrosion resistance. However, after long-term operation (especially over 10 years), corrosion of the inner wall generally occurs to form a corrosion product called "red rust", wherein three types of red rust (Type III rouge with complex components and strong adhesion, mainly comprising iron oxides such as Fe2O3, fe3O4, and possibly compounds containing elements such as silicon, chromium, and nickel) are most stubborn, and the generation of such red rust not only seriously damages the integrity of the surface passivation film, causes local corrosion such as pitting and intergranular corrosion, and more directly causes deterioration of water quality at the outlet of the system, and is manifested by exceeding of conductivity, total Organic Carbon (TOC) and particle number, and significantly increases risk of microorganism growth. At present, the traditional method for treating the intractable red rust mainly adopts a two-step process of acid washing firstly and then passivation, common acid washing liquid comprises nitric acid, hydrofluoric acid or mixed acid thereof (such as HNO 3 -HF), and ferric oxide is dissolved by utilizing strong acidity of the acid washing liquid, however, the strong acid washing has obvious defects that firstly, the acid washing has strong non-selective erosion effect on a stainless steel substrate, excessive corrosion on the metal surface is extremely easy to cause light loss, roughness and even new active corrosion points, the original metal color and luster and finish of the stainless steel cannot be kept, namely 'natural color' treatment cannot be realized, secondly, the two-step process flow is complicated, the system downtime is long, gaps are converted in steps after acid washing and before passivation, secondary pollution and flash erosion are extremely easy to occur on the exposed active metal surface, and new risks are introduced. Thus, there is a need in the industry for innovative approaches that overcome the above-mentioned contradictions. Disclosure of Invention The invention aims to provide a compound water-based working solution for cleaning and passivating the inner wall of a stainless steel pipeline and a use method thereof, and the core of the compound water-based working solution is to develop a novel compound medicament and a matched process, so that the intractable red rust can be efficiently disintegrated and removed on the premise of not damaging a stainless steel substrate, and meanwhile, a high-quality passivation film can be generated on the clean active metal surface in situ, the cleaning-passivating integration is realized, the natural color of the metal substrate is strictly maintained, and at least one of the problems can be solved. According to a first aspect of the invention, there is provided a compound water-based working fluid for cleaning and passivating the inner wall of a stainless steel pipeline, which is compounded from the following components: a) An organic acid complexing agent; b) A fluorine-containing inorganic acid dissolvent; c) An oxidizing inorganic acid passivating agent; d) Nitrogenous heterocyclic metal corrosion inhibitors; e) An anionic surfactant; the balance of water; The components cooperate with each other, so that the working solution can form a passivation film in situ and keep the original color of the metal substrate while the intractable red rust on the inner wall of the stainless steel pipeline is removed in the cyclic cleaning process. In some embodiments, the contents of the components in volume percent are respectively: 6-10% of organic acid complexing agent; 1 to 2.5 percent of fluorine-containing inorganic acid dissolvent; 2-4% of an oxidative inorganic acid passivating agent; 0.1 to 0.5 percent of nitrogenous heterocyclic metal corrosion inhibitor; the anionic surfactant is 0.05-0.2%. In some embodiments, the organic acid complexing agent is citric acid. In some embodiments, the fluorine-containing inorganic acid dissolving agent is hydrofluoric acid. In some embodiments, the oxidizing inorganic acid passivating agent is nitric acid. In some embodiments, the nitrogen-containing heterocyclic metalloid corrosion inhibitor is Benzotriazole (BTA). In some embodiments, the anionic surfactant is Sodium Dodecyl Benzene Sulfonate (SDBS). The core syne