Anti-rust knowledge-water-based anti-rust agent

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[Abstract] Water-based anti-rust agent is a temporary anti-rust material commonly used in industrial cleaning agents. With the development of manufacturing industry, new requirements have been put forward for its performance. This paper introduces the basic composition, mechanism and application method of water-based rust inhibitor, analyzes the research on water-based rust inhibitor in recent years, points out the problems existing in the current metal water-based rust prevention technology, and expects that the new water-based rust inhibitor should be efficient, green, multi-functional, can be used for storage and rust prevention.
Keywords: water-based antirust agent; inter-process antirust; sequestration antirust; antirust mechanism
0. Overview
Water-based rust inhibitor is a commonly used temporary anti-rust material, because of its water as the medium, the use of safe, convenient, easy to clean, has become one of the indispensable temporary anti-rust materials in the process of metal products.
The anti-rust of water-based anti-rust agent is greatly affected by the pre-treatment process, water quality, use environment such as region, climate, season, humidity, composition in the atmosphere and other conditions. The same water-based anti-rust agent will be used for different anti-rust conditions. Therefore, the current water-based anti-rust agent is mainly used for inter-process anti-rust in the processing of metal products.
1. Classification and standard
In GB 7631.6 (equivalent to ISO6743/8), RB, RH, RM and RP are all antirust materials with water as medium.
RB: Water-diluted liquid with a thin oil film, used for inter-process rust prevention.
RH: Water-diluted liquid with waxy to greasy film, used for rust prevention of finished products in warehouses. (Emulsified wax for rust prevention)
RM: Solvent or water-diluted liquid with wax to dry film, used to protect vehicle surface coatings. (Emulsion wax for protection)
RP: solvent or water-diluted liquid with peelable film, used for metal sheet protection to prevent scratches. (Peelable protective coating)
Because water-based rust inhibitor is usually based on the rust-proof object and rust-proof purpose and other specific circumstances of the preparation of temporary rust-proof materials, it is affected by the conditions of use, its research and development and used to seal rust-proof research is far less than rust-proof grease, there is no water-based rust inhibitor of the national standard and line standard.
2. Basic composition
Table 1 Basic composition of water-based rust inhibitor
Common Material Examples
1 corrosion inhibitor alcohol amine, fatty amine (soap), benzoate, carboxylic acid soap (or amide), muscle amine acid salt, imidazoline and its derivatives, phytic acid soap, benzotriazole and its derivatives, nitrite, tungstate, molybdate, phosphate, silicate
2 film forming agent synthetic water-soluble polymer, natural water-soluble resin, vegetable oil modified water-soluble compounds
3 pH regulator sodium carbonate, sodium hydroxide, potassium hydroxide, organic amine
4 Diluent water, ethanol
5 Other water softeners, colorants, olfactory regulators
Early water-based rust inhibitors usually use nitrite as the main anti-rust additive, adding sodium carbonate or alcohol amine compounds. This water-based rust inhibitor has low cost and good rust resistance to ferrous metals. Therefore, it has been widely used in inter-process rust prevention in the metal processing industry. As nitrite is suspected of environmental protection, advanced industrial countries have successively banned nitrite-based water-based rust inhibitors. After years of research and development in China, most of the current water-based rust inhibitors do not contain nitrite.
Water-based rust inhibitors are usually sold as concentrates and are used in proportion to the appropriate amount of water diluted according to the actual situation.
3. Principle of action
The anti-rust principle of water-based anti-rust agent can usually be summarized into the following categories:
(1) A dense oxide film is formed on the metal surface. The anti-rust additive in this type of anti-rust agent can react with the metal surface to form a layer of insoluble dense oxidation protective film, thereby preventing the anode process of the metal, slowing down or terminating the electrochemical process of corrosion, and realizing the protection of the metal. For example, water-based rust inhibitors containing molybdate and tungstate fall into this category.
(2) Formation of insoluble salt protective film on the metal surface. The anti-rust additive in this type of anti-rust agent can react with the metal ions dissolved on the metal to form an insoluble salt, which is deposited on the surface of the metal to form a dense protective layer to prevent the further dissolution of the metal and play a protective role, such as water-based anti-rust agents containing phosphates and silicates.
(B) Formation of a poorly soluble complex covering film. Most of the anti-rust additives in this type of anti-rust agent contain heterocyclic groups of elements such as N, O, and S. They can complex with metal atoms on the metal surface or metal ions near the metal surface, and form a layer on the surface of the metal. The insoluble complex protective film prevents the dissolution of the metal and plays an anti-rust role. Benzotriazole aqueous solution of copper protection belongs to this category.
(4) Formation of a physical adsorption film. This type of anti-rust agent usually contains water-soluble polymer film-forming agent, after the evaporation of water to form a thick protective film on the metal surface, to prevent the direct erosion of harmful gases in the atmosphere on the metal substrate, to achieve the metal rust.
In the water-based rust inhibitor formulation, a variety of anti-rust additives are usually used in combination, using the principle of positive synergy between additives, so as to achieve high anti-rust effect at low use concentration, therefore, the above-mentioned various anti-rust mechanisms may exist harmoniously in the water-based rust inhibitor.

4. Evaluation method
Since there is no national standard or line standard for water-based rust inhibitors at present, except for physical and chemical inspection items such as density and pH value, the rust prevention performance is usually carried out according to the method of water-based cutting fluid (GB/T 6144 or JB/T 7453), I .e. grade I gray cast iron is used for static constant temperature drip rust prevention test and lamination test, or cast iron powder method (JB/T 9189) is used.
5 Methods of Use
According to the requirements of the anti-rust object on the anti-rust period and the subsequent process, different water-based anti-rust agents and corresponding anti-rust processes can be selected. The examples of water-based anti-rust cleaning and anti-rust processes are as follows:

In the water-based anti-rust process should pay attention to the following factors:
Table 2 Main influencing factors of water-based rust prevention
Brief Description of Influencing Factors
1 cleaning metal workpiece on the residual processing fluid (oil), especially the processing fluid containing sulfur, phosphorus, chlorine and other extreme pressure elements, will seriously affect the rust resistance, so it must be thoroughly cleaned and removed, if necessary, the use of double or multi groove degreasing cleaning, to ensure the removal of dirt on the surface of the workpiece.
2 Rinse the workpiece by the cleaning agent to remove the oil and cleaning agent mixture, must be rinsed in addition to the net, usually the use of double tank flowing water rinse, to ensure that the rinse effect. Prevent secondary pollution.
3 Various ions in water quality, especially chloride ions and sulfate, have a great influence on the rust resistance of water-based rust inhibitors. Deionized water should be used to prepare water-based rust inhibitors. If tap water or other water is used, the corresponding rust resistance test should be made first.
4 packaging materials for the process of water-based rust, no packaging. The workpiece treated with water-based anti-rust liquid can be sealed and anti-rust after proper encapsulation, but the corresponding supporting anti-rust process must be adopted.

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