Coating for producing tubular high-silicon cast iron positive electrode and preparation method of coating

Abstract

The invention discloses a coating for producing a tubular high-silicon cast iron positive electrode. The coating comprises the following components in percentage by mass: 25-30 percent of kieselguhr, 2-5 percent of expanded perlite powder, 5-10 percent of zircon-quartz powder, 2-5 percent of sodium bentonite, 3-5 percent of silica sol, 2-4 percent of dextrin, 0.1-0.3 percent of k-12 lauryl sodium sulfate and 50-55 percent of water, wherein the total amount of the kieselguhr, the expanded perlite powder and the zircon-quartz powder is greater than or equal to 37 percent and less than or equal to 42 percent, and the total amount of the sodium bentonite, the silica sol and the dextrin is greater than or equal to 7 percent and less than or equal to 10 percent. A preparation method of the coating comprises the following steps: (1) smashing the raw materials; (2) performing dry mixing and water mixing; and (3) finally adding the k-12 lauryl sodium sulfate, and uniformly stirring. Compared with the prior art, the coating disclosed by the invention has the characteristics of high adhesive force to a mold, high flowability, good high-temperature resistance, good ventilation property and easiness in cleaning and enables bulges (or a pitted surface) on the surface of a product to be uniformly distributed.

Description

technical field [0001] The invention belongs to the technical field of preparation of cathodic protection materials, in particular to a coating for producing high-silicon cast iron tubular anodes and a preparation method thereof. Background technique [0002] Cathodic protection is an electrochemical protection technology to prevent metal corrosion. Its principle is to apply an external current to the surface of the protected metal structure, and the protected structure becomes a cathode, thereby inhibiting the electron migration that occurs in metal corrosion, avoiding or reduce the occurrence of corrosion. There are two types of cathodic protection techniques: impressed current cathodic protection and sacrificial anode cathodic protection. [0003] Due to the advantages of low consumption rate, long service life, large allowable current density, wide protection range, small grounding resistance, stable polarization potential and high utilization rate, high silicon cast ir...

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Problems solved by technology

[0007] In the prior art, there are coatings used for centrifugally preparing metal pipes. Chinese invention patent CN1520951 discloses a centrifugal casting high-alloy furnace tube metal mold coating and its method. The ingredients are: zircon powder 100KG, silica sol 5-15KG, fluorite powder 2 Add ~6KG, 3~8KG of bentonite into the wheel mill, dry mix for 15 minutes, add 80~200KG of cellulose dissolved in water, 80~200KG of polyvinyl alcohol and 5KG of water, and mix and grind for 3 hours; add 5~15KG of silica sol and mix and grind After 30 minutes, due to the difference of the binder, the low-temperature strength of the coating increases after spraying; due to the addition of cellulose and polyvinyl alcohol, the plasticity of the coating at low temperature increases, which improves the ability of the coating layer to resist erosion during pouring and The ability of metallic properties to resist vibration during high-speed operation; but when this coating is used for centrifugal casting radiant tubes, the coating has adhered to the surface of the radiant tube and is not easy to remove, which affects the radiation heat transfer effect of the radiant tube. If it is used to prepare high-silicon Cast iron tubular anodes affect the electron diffusion of high-silicon cast iron anodes and affect the anti-corrosion protection effect

Chinese invention patent CN1109395 also discloses a kind of centrifugal casting bucket coating, which is composed of base material, auxiliary material and water. It is 100-250% of the total weight of (base material + auxiliary material), and the chemical composition (weight %) of (base material + auxiliary material) is: any one of quartz or zircon: 55-95%, kaolinite Type refractory clay: 3.5-40%, water glass or silica sol: 1-5%, sodium carbonate or caustic soda: 0.1-0.5%, sodium hydroxymethyl cellulose: 0.01-0.1, the particle size requirements of the refractory clay: The particles of <10μm are not less than 45%, and the particles of <1μm are not less than 1.5%. However, when this coating is used for centrifugal casting of high-silicon cast iron tubular anodes, the coating is also easy to adhere to the surface of high-silicon cast iron tubular anodes, and it is not easy to Cleaning will affect the electron diffusion of high-silicon cast iron anode and affect the anti-corrosion protection effect

Chinese invention patent CN1116141 discloses a centrifugal casting tubular coating, its composition and weight ratio are: 100 parts of base material, 100-120 parts of water, 5-8 parts of bentonite, 0.15-0.3 parts of Na 2 CO 3 , can also add 0.1~0.3 parts of anionic surfactant, wherein, the base material is diatomite and quartz powder, the base material adopts the calculated weight, the remaining components adopt the actual weight, the relationship between the calculated weight of the base material and its actual weight For: W (count) 硅藻土 =3W (real) 硅藻土 , W (count) 石英粉 =W(real) 石英粉 , the coating has good suspending property, low gas generation, good demoulding property, hot metal erosion resistance and heat insulation and fire resistance performance, but it is not easy to be on the outer surface of the tube when it is used for centrifugal casting of high-silicon cast iron tubular anode Obtain evenly distributed pitted surface, and if there is quartz powder, the coating is easy to adhere to the outer surface of the high-silicon cast iron tubular anode, which affects the electron diffusion of the high-silicon cast iron anode, thereby affecting the anti-corrosion protection effect

Chinese invention patent CN1775414 also discloses a formula and process for making coatings for centrifugal casting high-alloy furnaces for nuclear power plants. Its composition (calculated on the basis of 100kg): microsilica powder 30% + diatomite 70% 16-25kg / dihydrogen phosphate 3-5kg of aluminum, 3-5kg of bentonite, 0.5-2kg of PVA, and the rest are zircon powder; the production method: first mix 3-5kg of bentonite with 30% of silica powder + 70% of diatomite 16-25kg with a ball mill , add an appropriate amount of water and stir for 1 hour, then add zircon powder and stir for 1 hour, then add 3-5kg of aluminum dihydrogen phosphate and 0.5-2kg of PVA solution and stir for 2 hours to obtain the coating; but for centrifugal casting high silicon For cast iron tubular anodes, it is not easy to obtain evenly distributed pockmarks on the outer surface of the tube, which will affect the electron diffusion of high-silicon cast iron anodes and affect the anti-corrosion protection effect

Japanese patent JP5401920-A also discloses a coating for centrifugally cast steel (or nickel-based alloy) pipes, which contains B 4 C, it is easy to form a layer of boron-containing hardened layer on the surface of the cast pipe, which is beneficial to improve the wear resistance of the cast pipe surface, but it is not easy to obtain uniformly distributed pockmarks on the outer surface of the pipe when used for centrifugal casting of high-silicon cast iron tubular anodes

Invention patent RO95387-A also discloses a refractory coating for centrifugal steel casting, containing 1.5-5% bentonite, 0.3-1.5% starch, 2-5% water glass, 0.1-0.2% phenol or formaldehyde solution, but the human body After inhaling phenol, it will cause dyspnea and headache, and it will irritate the eyes, and formaldehyde is also a pure venom, which can be combined with protein. Bronchial asthma occurs, because the paint is harmful to the body, it is not suitable for centrifugal casting of high-silicon cast iron tubular anodes

Chinese invention patent CN101502868 is a centrifugal casting radiant tube coating and its preparation method, which discloses that the mass percentage composition of the coating is: 25-30% diatomite, 5-10% zircon powder, 1.0-1.2% titanium powder, 1.5 -1.8% iron powder, 4.5-5.0% sodium bentonite, 2.0-2.5% polyvinyl alcohol, 0.8-1.0% sodium alginate, 3.5-4.0% silica sol, 0.8-1.0% sodium dodecylbenzenesulfonate, 0.05-0.08% silane, 46.82-49.95% water, of which 35% ≤ diatomite + zircon powder ≤ 37%, 2.7% ≤ titanium powder + iron powder ≤ 2.9%, 8.0% ≤ sodium bentonite + polyvinyl alcohol + Sodium alginate ≤ 8.2%; the preparation method is: first add 200-280 mesh sodium bentonite, 200-280 mesh zircon powder, 200-280 mesh titanium powder and 200-280 mesh titanium powder into the wheel mill according to the above ratio Dry mixing for 15-25min; then add sodium alginate, sodium dodecylbenzenesulfonate, silane, polyvinyl alcohol and water in sequence according to the above ratio, and mix and grind for 180-240min; then add silica sol and mix according to the above ratio Grinding for 30-40min; finally, sieve the mixed and milled paint through an 80-100 mesh sieve to remove impurities; however, when it is used for centrifugal casting of high-silicon cast iron tubular anodes, the high temperature resistance is not enough, the surface is prone to casting defects, and it is not easy to The outer surface of the tube gets an evenly distributed pitting

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