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Economics of surface coatings on metals are discussed with emphasis on surface preparation, especially when large scale coating operations are conducted. Relative cost and other parameters affecting the choice between manual and machine blasting are considered, including the area cost of surface preparation, health and safety factors, incidental pollution, and other variations. Advantages of high build surface and multi‐purpose primer application are related along with comparisons of cost between initial and manual recoating of structures after erection. Importance of proper coating maintenance is emphasised. Economic case histories are given, including large scale surface preparation of tank plates and piping, differences between sand abrasive and centrifugal blasting, factors related to intercoat adhesion, cost of Zn rich with epoxy or alkyd topcoats, and the high cost of repainting when scaffolding is necessary. Regulations on surface preparations, ecological controls, and safety are discussed. Two coat simplified systems are recommended, along with automatic and semiautomatic surface preparation when the size of the job makes either one possible. Tabulated data on area costs of various modes an locations for surface preparation and coating costs for various metal configurations are provided.
The use of an observational approach in conjunction with isolation techniques for campylobacter and salmonella detection has facilitated a detailed evaluation of the risk…
The use of an observational approach in conjunction with isolation techniques for campylobacter and salmonella detection has facilitated a detailed evaluation of the risk of cross contamination during food preparation. Identification of suspected exposure routes has linked naturally contaminated raw foods with important food‐handling malpractices, contaminated contact surfaces and ready‐to‐eat foods. In a model domestic kitchen, 29 per cent of food preparation sessions resulted in positive campylobacter isolations from prepared salads, cleaning materials and food‐contact surfaces. Typing results showed that specific campylobacter strains isolated from prepared chicken salads were the same as the strains isolated from the raw chicken pieces, indicating microbial transfer during food preparation. Data obtained from this study can be used for exposure assessment, risk management and in the development of consumer risk communication strategies.
Surface preparation—Reasons and Methods To determine the reason why we prepare the metal surface, we first consider the end result we wish to achieve. Exposure to the…
Surface preparation—Reasons and Methods To determine the reason why we prepare the metal surface, we first consider the end result we wish to achieve. Exposure to the elements will rapidly corrode metals and lead to destruction by erosion, particularly in salt‐laden air. We must, therefore, bond on to this surface a complete barrier to external destruction by means of a protective coating. (We do not ‘paint the boxes’, we apply a protective coating).
Conventional processes for cleaning, stripping and surface preparation mainly use solvents or abrasives which can be harmful for the environment, and can also damage the…
Conventional processes for cleaning, stripping and surface preparation mainly use solvents or abrasives which can be harmful for the environment, and can also damage the surface of the material. Moreover, the use of these products generates a large quantity of waste that needs to be reprocessed or discarded. In many cases, laser is the solution to these problems. Its possibilities are still under‐exploited but they are growing with the improvement of the performances of the CO2, YAG and Excimer lasers. This paper describes the laser cleaning process and the benefits which can be obtained.
At the request of the Netherlands Corrosion Centre (N.C.C.), the Corrosion Committee IVa of the Metaalinstituut T.N.O., which has for many years been carrying out research…
At the request of the Netherlands Corrosion Centre (N.C.C.), the Corrosion Committee IVa of the Metaalinstituut T.N.O., which has for many years been carrying out research on the protection by paint of steel structures in the atmosphere, drew up general directives for such protection. The surface preparation section was undertaken in collaboration with the Vereniging Metaalbeits, and is being published in CORROSION TECHNOLOGY in two parts, the second part appearing in April.
Preparation of metal surfaces for subsequent coating operations may be achieved by a number of methods but, for production lines, the use of liquids is probably the most economic technique. Surface preparation of a metal aims at producing the most suitable metal surface for the selected coating programme and, despite ideas to the contrary, this may not necessarily mean a perfectly clean surface.
The purpose of this paper is to examine the effects of the welding deformation and surface roughness in cold pressure welding on the tensile strength and the fatigue…
The purpose of this paper is to examine the effects of the welding deformation and surface roughness in cold pressure welding on the tensile strength and the fatigue strength of joined sheets. Additionally, the paper seeks to analyse the hardness variations and microstructures at the welding interface.
Cold pressure welding is a method of joining similar or dissimilar ductile metals. It can be applied by bringing into close contact the surfaces of virgin metal specimens that appear due to the breakdown of the surface layers caused by bulk plastic deformation. Cold pressure welding is applied to test parts without too long a delay after the preparation of surfaces. The application of welding in 10 min affects importantly the weld strength. As this time is increased, the weld strength of the joints is decreased. The determination of deformation amount is found by determination of the reduction (R) at the total thickness of the two parts after the welding process.
The weld strength increases as the surface roughness and weld deformation of the joined sheets increase. The length of bond zones increases with increasing deformation. Therefore, the weld strength of parts depends on the length of bond zones. Then, there is an effect of surface roughness on the welding strength. Joined sheets show resistance to little fluctuating tensile stress. It is observed that the parts rupture from the welding‐interface hardness values are about the same at interfaces of sheets having different surface roughness and equal deformation (60 per cent). But, if it is considered that hardness of aluminium material purchased is about 53 HV, it can be said that the hardness increases in joined parts because of local hardening during deformation in cold pressure welding method as lap welding. Bond formation at interfaces of joined sheets having Ra=5 μm surface roughness and deformation ratio 60 per cent is shown to be successful in the microstructure photo.
Surface roughness and deformation values can be increased in further studies.
The paper offers insight into the effects of surface roughness on weldability.
Perhaps it is true to say that the correct time to repaint is before it becomes necessary! Unfortunately, the economics of modern industry are such that even in efficient industrial organisations, maintenance is not always rated highly in the priorities of budget expenditure. The ideal at which to aim is the gradual build‐up of paint thicknesses, achieved only by repainting at fairly regular intervals, while the original paintwork is still in good condition. If repainting is carried out at this time, preparation can, in the main, be limited to cleaning and perhaps rubbing down of painted surfaces with little necessity for large‐scale preparation of the steelwork itself.
Examines the use of power beams to prepare surfaces prior to adhesive bonding. Describes the current surface treatments available and discusses their limitations. Outlines how power beam techniques for surface modification of polymeric and metallic adherends has the potential to overcome many of these problems. Also looks at the emerging technology of using radiation‐curable adhesives based on ultraviolet, visible light and electron beams, which have the advantages of fast rates of cure, improved quality of finished products and the absence of any volatile organic compounds.
Due to problems experienced at the deburring stage of drilled 0·013 in. diameter holes, where the holes became blocked with deburring brush fibres, it was necessary to…
Due to problems experienced at the deburring stage of drilled 0·013 in. diameter holes, where the holes became blocked with deburring brush fibres, it was necessary to replace the use of traditional deburring techniques for the preparation of these drilled holes prior to electroless copper plating. In order to achieve this, a jet pumice machine was purchased and trials were conducted using various grades of pumice powder and different machine parameters. The purpose of these trials was to determine the optimum machine parameters for the task, such that burr‐free hole peripheries were achieved in conjunction with a surface finish suitable for electroless copper plating prior to dry film lamination.