ZERMEG II – Zero emission retrofitting method ... - Fabrik der Zukunft

5 Features of common galvanising processesA galvanising process typically consists of many steps, each with a clear and unique function.The process can be divided in four parts, called the pre-treatment, the electroplatingprocess, the after treatment activities and support functions. In each step there can be useddifferent solvents, process chemicals or temperatures.5.1 Pre-treatmentThe surface of the components that shall be galvanised are polluted with organic pollutants,such as oils and greases, scales, swarfs or metal-oxids from earlier production process steps.The organic pollutants result i.e. from cooling lubricants or anticorrosive oils and may be ofmineral or natural nature. Scales and swarfs result from the production process and metaloxidesare the result corrosion of pure metal surfaces in contact with air.All these pollutants have an impact on the quality of the galvanising processes and must beremoved.5.2 DegreasingOil and grease downgrade the efficieny of the following process steps, because the organiccomponents adhere very strong to metal surfaces and so disable the effect of the usedchemicals. So the first process step in most electroplating plants is the removal of oil andgrease.Most common are two methods – the aqueous and the solvent degreasing.Aquaous degreasing uses usually alkaline or neutral solutions, but maybe acidic as well. Themain components of degreasing solutions are alkalis or acids, silicates, phosphates andcomplexing and wetting agents, i.e. tensides. The solution can work either as stableemulsions or demulgating system. The temperature range is usually 40-90°C and dependson the stability of the inserted agents.Solvent degreasing uses the efficiency and universal applicability of different organicsolvents. Most common are chlorinated hydrocarbons, alcohols, terpenes, ketones, mineralspirits or hydrocarbons. The organic solvents are maily incombustabily and the componentsdry very fast.There are two main types of processes, which are cold and vapour cleaning. Cold cleaninguses a fluidic solvent whereas in vapour cleaning the solvent is gaseous.8