| Cleaning is a technology with a long history. In ancient times, plant ash, dissolved to form alkaline aqueous solution, was used for clothes washing. With the development of productivity and technology, cleaning has become a more professional technology with a wider range of knowledge.In the cleaning of metallic parts, it is necessary to remove the antirust oil, cutting fluid and other fouling from the surface of metal before further treatment. The metal surface cleaners and degreasers, which are widely used, are consisted of builders(e.g. alkali or phosphate) and surfactants(e.g. nonyl phenol or octyl phenol). Besides, the operating temperatures are maintained above 80 o C, requiring additional energy consumption. The phenol-containing surfactants are of bio-toxicity and hardly degradable, thus remaining in water for a long time. Furthermore, without thoroughly treatment, phosphorus remained in effluent would flow into the water bodies, leading to eutrophication.In this research on phosphate-free degreaser applied to the steel pieces or parts, the properties of several phosphate-free and phosphate-substitute builders are compared in terms of the efficiencies and binding force for calcium and magnesium through a series of tests.Eventually, the sodium salt of maleic anhydride-acrylic acid copolymer(DG) and modified organic carboxylic acid of silicate were chosen as builders. These two phosphate-free builders could be the fundamental solution to the problem of phosphorus in sewage. In addition, an eco-friendly surfactant(EH) consisting of modified alcohol ethoxylate, which is synthesized by vegetable oleyl alcohol, was used as surfactant. As a key component, EH had better wettability and detergency comparing with other widely-used surfactants such as primary alcohol ethoxylate and nonyl phenol polyoxyethylene ether. The compound of anionic and nonionic surfactants such as alkyl polyglucoside showed higher detergent efficiency and lowered down the operating temperatures to 60 o C, thus minimizing the energy demand.According to the experimental results of practical manufacture and formula optimization,the optimum formula of phosphate-free degreaser applied to steel pieces or parts was as follow(in mass percentage): 20% sodium hydroxide; 33.8% sodium carbonate; 4.6% sodium metasilicate pentahydrate; 23.1% DG; 4.6% lauryl sodium sulfate(K12); 2.5% EH; 1.5%TO-89; 1.5% NEODOLTM; 2.5% ST-90; 3.5% anhydrous sodium sulphate. Cleaning efficiency, cleaning performance under low and medium temperature, stability in high alkalinity, service life, adaptability to various oil contaminations and other parameters had been taken into consideration. Moreover, the optimum processing condition was as follow:theconcentration of degreaser was 4%~5%(in mass percentage); the operating temperature was maintained between 50 o C and 65 o C; immersion or ultrasonic cleaning was applied; cleaning time was about 3min to 10min; rinse in flowing water for one time then in still water for twice.Compared with BH-11(degreaser applied to steel pieces or parts at low and medium temperature, commercial product from Guangzhou Etsing Plating Institute), this phosphate-free degreaser had better cleaning effect, lower COD value and longer working life.After this phosphate-free degreaser having been applied for more than 6 months in an electroplating company focused on chemical nickel-plating, it rendered following advantages:(1) showing higher cleaning efficiency and more thoroughly cleaning effect for complex parts;(2) obtaining better cleaning ability and adaptability to different oil contaminations;(3)simplifying the process, no treatment for phosphate in effluent being required, saving the treatment cost;(4)extending working life, reducing the consumption of degreaser, bringing down the production cost;(5)being more biodegradable with lower COD value, decreasing the difficulty of operation. |
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