As basic chemical materials, many products produced by our company are used widely in the aspects of electroplating and corrosion protection. Because of strong oxidizing property, potassium permanganate and sodium permanganate can be used widely for building waterproofing, metal surface treatment, plastic electroplating, ect in daily life. Chromic anhydride produced can be used to produce chromic compounds, and widely used for corrosion protection of woods additionally. Chrome is characterized by chemical stability and high hardness and wear resistance. Chrome oxide green, chromic anhydride, etc produced by our company can be used widely for electroplating, e.g., chromeplating of bicycle, sewing machine, semisteel watch, torch, daily hardware part, instrument and meter.
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| Multifunctional efficient building waterproofing agent | As one of major components of multifunctional efficient building waterproofing agent, potassium permanganate can make the waterproofing agent characterized by good waterproofness, short curing time, mold proofing, damp proofing, protection against acid rain corrosion, resistance to weather, color-keeping, etc and not affected by external environment during construction. |
waterproofing agent: according to the following proportion (mass ratio), weigh solid components such as sodium chloride, potassium permanganate, potassium alum, sodium carbonate, bluestone, ferrous sulphate, urea and boracic acid, mix them evenly and grind them to fineness as low as 80 mesh, heat the water to 100℃, dissolve finely-ground solid raw meterials in the water, add the water glass in the water, and stir the solution at a speed of 80~100r/min for above 30min, getting a colloidal product who is colorless and whose PH value is 12 and relative density is 1.04. Raw materials: sodium chloride/potassium permanganate/potassium alum/sodium carbonate/bluestone ferrous/sulphate/urea/boracic acid/water glass/water 1# 3.08/3.4/9.0/2.9/5.5/7.3/7.1/1.5/765/178 |
| Corrosion protection of woods | react with other metal salt to generate a water-insoluble compound which plays a good role in fixing texture of wood so as to reduce the corrosivity of agent for metal and inhibit the corrosive action of other salt. However, bluestone can not only increase toxicity but also enhance leaching resistance obviously. CCA is the most famous water-soluble compound preservative in the world at present. After impregnating wood, CCA can take effect quickly, generating water-insoluble compounds such as copper chromate, copper arsenate, chrome arsenate and chromium chromate which can be fixed on wood fibre quickly and hardly scoured off by rainwater or soil moisture so as to protect the wood from being eaten by insects like termite, prevent bacteria and mold from multiplying resulting in biodegradation, and prolong the service life of wood tens of times. It is a kind of quickly-fixed preservative and has high bactericidal activity (1.3-3.0kg/m2) and high resistance to termite and shipworm. After being treated with it, the wood is celadon. |
CCA preservative used widely in the world at present is classified by constituent contents into CCA-A type, CCA-B type and CCA-C type. Constituents of all types of CCAs are as shown as follows: |
| Metal surface treatment |
1. Remove the iron impurities in the bath (zinc plating bath): use potassium permanganate ferrous oxide to generate flocculent ferric hydroxide easily to be removed by precipitation. 2. Quicken the surface passivation of aluminium alloy material by means of potassium permanganate. Potassium permanganate, instead of hexavalent chrome, can be used for metallochrome passivation in the passivation process of aluminium and its alloy and also be used as additive for chemical polishing of aluminium and its alloy.。 3. Chrome oxide green is also called as chromic oxide or chrome, its Moh’s hardness is 8.5-9, approaching that of corundum (Al2O3), only lower than that of diamond and higher than thoes of quartz，topaz and zircon. It is very stable for light, atmosphere and corrosive gas (H2S, SO2, etc) and has good weathering resistance. |
1. The iron impurities in zinc plating bath are co-deposited in ferrum in zinc, with difficulty in passivation, and excessive potassium permanganate must be dosed in order to remove ferrum thoroughly, but remaining potassium permanganate wll also break the brightener added later. Therefore, after precipitation and filtration for removal of iron impurities, about 1mL 30% hydrogen peroxide should be added in the test to reduce the residual potassium permanganate. And after they act for a while, sample the liquor for test and adjust the brightener. 2. E.g., Sheng-Song Ge, et al have generated black chromium-free conversion firm in KMnO4 solution. KMnO4 concentration in its solution is 6g/L. After oxidation two times, the corrosion resistance of aluminum alloy has been enhanced. The film is mainly composed of Al2O3 and various oxides of manganese. Generally speaking, hypermanganate is not a good kind of corrosion inhibitor for aluminium and its alloy but can accelerate the corrosion. 3. Chrome oxide green is a kind of chemical material used widely in metal surface treatment industries like polishing, burnishing, phosphorization, sand blasting and electroplating. |
| Plastic electroplating | Potassium permanganate can be used for chemical coarsening treatment of some materials in the plastic electroplating and also to metallize walls of circuit board manufacturing holes. The method that active groups are formed on plastic surface can be utilized to absorb metallic ions so that the surface has catalytic activity, a bit similar to manufacturing of printed board. For a kind of thermosetting allyl-dimethyl-phenylate alkene resin, after the surface is coarsened with potassium permanganate and sodium hydroxide, use sulfuric acid for sulfonation to exchange sulph as positive ion with base groups and introduce them on the surface so as to absorb the copper ions. Soak this plastic with surface catalytic activity in the bluestone solution, and reduce the immersion liquid by sodium borohydride to obtain the chemical plating copper layer. | Optimum process condition of potassium permanganate coarsing: 20g/L potassium permanganate, coarsing temperature 70℃, coarsing time 40min. (Sun Dun, He Jianping, et al. Potassium Permanganate Pretreatment Process of ABS Plastic Electroplating [J]. Materials Protection, 2009, 42(12) |
| Protection and decoration of hardware parts |
1) In air, chrome is oxidized easily to form a thin and dense oxide film. This film has good mechanical strength and high transparency and can keep chrome metal tarnishproof for long term. 2) Because of good chemical stability and strong erosion resistance (without rusting and depigmentation), chrome cannot be affected by many kinds of acid. 3) It has high hardness and wear resistance and its relative hardness is 9, only lower than that of diamond; 4) It has good metal luster with offwhite and good reflectivity; 5) It has high melting point; These characteristics cannot be comparable to those of many metals, so it is often used as basic of other coatings to resist to all kinds of corrosive media and applied widely in all aspects of industrial products and daily products. |
Type and usage of chromeplating There are many types of chromeplating processes which can be classified by usage as follows.
① Protective-decorative chromeplating Protective-decorative chromeplating commonly known as decorative chromium coating, thin, bright and beautiful, is usually used as outermost layer of multilayer electroplating. For protection, an intermediate layer must be plated on zinc base or iron and steel substrate first and then 0.25 to 0.5μm layer of chrome on the bright intermediate layer. Common processes include Cu/Ni/Cr, Ni/Cu/Ni/Cr, Cu-Sn/Cr, etc. After being plated with decorative chromium coating on the surface, the polished product can obtain blue and silver specular gloss and cannot be faded in atmosphere durably. This sort of coating is used widely for protection and decoration of parts and components of automobiles, bicycles, sewing machines, clocks and watches, instruments and meters, daily hardware, etc. The decorative chromium layer polished has high reflectivity and can be used as a retroreflector.
Microporous or micro-crack chromeplating on multilayer nickel is an important approach to reduce overall thickness of coating and obtain high corrosion-resistant protective-decorative system and also a development direction of modern electroplating process. ② Hard chromeplating (wear-resistant chromeplating) The coating has very high hardness and wear resistance, and can prolong service life of workpieces, e.g., cutting and drawing tools, pressing dies and casting moulds from various materials, bearings, shafts, gaugest and gears, and also be used to repair worn parts to dimensional tolerance. Hard chromeplating is ussually 5 to 50μm thick and can be determined as needed, sometimes up to 200 to 800μm. No intermediate layer is required for hard chromeplating of iron and steel parts, and if corrosion resistance is required specially, different intermediate layer can be used. ④ Milky chromeplating The chromeplating layer is milky with low glossiness, good toughness, low porosity, delicate colour and the hardness lower than that of hard chromeplating or decorative chromeplating, but high corrosion resistance, so it is used widely for panels of gauges and instruments. In order to enhance its hardness, another layer of hardness chrome can be plated on the surface of milky chrome coating, i.e., double chrome coating combining characteristics of milky and hard chrome coatings, mostly used for parts with high requirements for wear resistance and corrosion resistance. ⑤ Spongy chromium plating (microporous chromeplating) The chrome coating is characterized by fine cracks. After hard chromeplating, the surface is spongy-treated mechanically, chemically or electrochemically to further deepen and widen the crack net. Grooves spread over the surface of chrome coating, not only having characters of wear resistant chromeplating but also keeping lubricating medium effectively, avoid running without lubrication and enhancing friction resistance and wear resistance of workpiece surface. It is usually used for surface plating of sliding friction pieces under high stress, e.g., inner chamber and piston ring of internal-combustion engine cylinder barrel. ⑥ Black chromium plating Black chrome coating has uniform luster, good decoration and good extinction; high hardness (130 - 350HV), and the wear resistance 2 to 3 times higher than that of bright nickel under the same thickness; the corrosive resistance as same as that of common chromeplating, mainly depending on thickness of intermediate layer. With good heat resistance, it cannot be faded at below 300℃. Black chrome coating can be plated directly on surfaces of iron, copper, nickel and stainless steel. In order to enhance corrosive resistance and decorative effect, copper, nickel or copper-tin alloy can also be used as base on whose surface a black chrome coating is plated. A black chrome coating is used widely for plating of parts of aviation instruments and optical instruments protection and decoration of solar absorption panel and articles of daily use. |
| Surface chromeplating | Because chrome has very high hardness, the surface can be resist to high temperature above 500℃, corrosion, acid and wear with enhanced hardness after being chromeplated. The chromeplating is applicable to all kinds of materials such as metals, resin, plastics (ABS,expanded plastic and recycled plastic), glass (crystal), ceramics, acrylic, wood, cement, phosphorus and magnesium. |
Main raw materials for chromium electroplating: chromic anhydride CrO3 120-200g/L; in chromeplating process, the electrolyte is ususally prepared with distilled water, and sulfate radical shall be removed from chromic acid by barium carbonate in the conditions that operating temperature is lower than 40℃, electroplating time is 10-30min, anode is Pb or Pb-Sn alloy and undercoat is copper or nickel. Simple process flow of chromeplating: surface cleaning - oil removal - activation (chromic anhydride) - chromeplating (hydrofluoric acid is often used for acid treatment in pretreatment before plating); A. Common chromeplating solution contains chromic anhydride and sulfuric acid; B. Compound chromeplating solution mainly contains chromic anhydride, sulfuric acid and fluosilicic acid; C. Self-adjusting chromeplating solution mainly contains chromic anhydride, sulfuric acid, strontium sulfate and potassium fluosilicate; D. Tetrachromate bath mainly contains chromic anhydride, chrome, sulfuric acid, sodium hydroxide and potassium fluosilicate; E. Trivalent bath mainly contains chromic chloride, with complexing agent, chlorate, boracic acid, etc added; F. Hard chromeplating solution contains chromic anhydride, sulfuric acid, CS-additive, trivalent chromium, etc; G. Black chromium plating solution contains chromic anhydride, sodium nitrate, boracic acid, fluosilicic acid, etc. |
