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This paper aims to investigate the corrosion behavior of zinc in a typical hot and dry atmosphere. It proposes the dynamic corrosion for different exposure periods. Results can provide the basic data and corrosion mechanism of zinc in such environment.

In this paper, the authors investigated the corrosion behavior of pure zinc exposed in the typical hot and dry environment in Turpan for one-four years, which has never been studied. Scanning electron microscopy, laser scanning confocal microscopy, electron probe micro-analyzer (EPMA), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) were conducted to measure the corrosion morphology and products of zinc. Finally, combining electrochemical impedance spectroscopy and scanning Kelvin probe techniques, the corrosion mechanism of zinc in Turpan was examined.

The thickness loss of the zinc followed an exponential law with respect to exposure time: D = 3.17 t^0.61, and both of the rust layer resistance and the charge transfer resistance increased with exposure time. The corrosion products mainly comprised ZnO, Zn(OH)₂, Zn₅(CO₃)₂(OH)₆, Zn₄SO₄(OH)₆·5H₂O and Zn₁₂(SO₄)₃Cl₃(OH)₁₅·5H₂O. The Kelvin potentials shifted toward the positive direction from −0.380 to −0.262 V (vs saturated calomel electrode [SCE]) when the exposure time extended from one to four years and the distribution of the corrosion products became more and more uniform.

The corrosion behavior of pure zinc in the typical hot and dry environment in Turpan has not been studied. The dynamic corrosion for different exposure periods was obtained. The corrosion products were systemically investigated via energy-dispersive X-ray spectroscopy, EPMA, XPS and XRD.

Studere Corrosion has been described as a transformation process in which a metal passes from its elementary form to a combined condition. It includes wet and dry corrosion; the former requires an aqueous environment and the latter is oxidation. Deterioration of the metal due to physical causes is not called corrosion, but is known as erosion, galling, wear, etc, depending upon the material and the conditions. Corrosion is the result of the metal chemical or an electrochemical reaction with its environment. Sometimes the chemical reaction is accompanied by physical deterioration, as in fretting corrosion. It should be noted here that the term corrosion is only applied to metals; non‐metals rot, crack or erode. Also it should be appreciated that only ferrous metals can ‘rust’, i.e. form hydrous ferric oxides.

Although a sheet of viscose film, such as cellophane, is so compact in structure as to be quite airtight, experimental work has shown that water vapour can evaporate as quickly from a vessel closed with it as from the open container. A wrapper composed of viscose film can be rendered impermeable to moisture vapour by covering the surfaces with a very thin layer of moisture‐proof transparent coating which often contains, as an essential ingredient, a small quantity of wax. It is wrappings of the latter “ moisture‐proof ” type which are normally used round cigarette cartons and often round biscuits and sweet packages. Unbroken films of wax are resistant to the passage of moisture vapour, and waxed papers are therefore largely used for the protection of foodstuffs. Not all waxed papers, or so‐called moisture‐vapour‐proof transparent wrappings, are satisfactorily impermeable to moisture vapour, and it is essential to test such materials to determine their actual protective powers. While complete protection against moisture exchange is advisable for most types of goods liable to dry out or for those which will deliquesce, it should be realised that there may be other factors that will prevent their being used. Some goods coated with cane sugar are found to keep best if in packings where they can “ breathe.” If, owing to a rise in temperature, the atmosphere in the moisture‐vapour‐proof wrapping should become saturated with moisture vapour, this would be deposited in droplets on the surface of the goods if the package were suddenly cooled. A dilute solution of sugar might be formed at the point of deposition, which would then be a favourable medium for the growth of aerial moulds and micro‐organisms. In many cases wrongly wrapped foods betray their deterioration by easily apparent signs, such as the hardness of bread, the stickiness of sweets or the odour of putrificd material. It is, however, quite possible for a loss in quality to occur which is only noticeable in flavour deterioration when the article is consumed, and an important instance of this is tea. Care must be taken that the wrapping itself does not impart a foreign flavour to the foodstuff packed in it, or induce one through permitting or accelerating chemical changes, such as oxidation (development of rancidity). Some of the transparent moisture‐vapour‐proof wrappings on the market have a strong flavour liable to contaminate goods wrapped in them, as have some waxed papers and ordinary “ boards ” used for cartons. Printing inks and adhesives used on cartons may also affect the flavour and odour of foodstuffs, unless properly chosen and properly used on the cartons. These odours will penetrate wrappers if the latter are not airtight, and instances are known where really expensive articles of food have been spoiled in flavour because strong‐smelling strawboards have been used as the foundation of the very elaborate and decorative boxes in which the foodstuff was packed. Rancidity development in fatty foods may be accelerated in several ways. It is well known that sunlight promotes the formation of rancidity, and fatty foods in ordinary transparent wrappings may deteriorate on this account. Attempts have been made to produce coloured transparent wrappers which will absorb the active light rays, and so prevent rancidity developing while at the same time allowing the goods wrapped to be visible. Some of these wrappers were so dark in colour that they were valueless for display purposes, but, according to advertised claims, some golden yellow transparent wrappers of good transparency and protective power are now available. There are available, however, wrappers treated with anti‐oxidants of the oat‐flour type which are claimed to arrest the development of surface rancidity of fatty foods packed in them. The last generation has seen the advent of scientific control and development in the catering business. Individual restaurants or hotels cannot afford to employ chemists, and with the exception of the large organisations owning a series of restaurants, the hotelier or restaurateur has to rely on the efforts of consultants or on the makers of the plant and machinery installed in his establishment. This help has been very valuable particularly as the amount of mechanical aids in restaurant kitchens has become during the last half century very considerable. Such devices as mechanical beaters or whippers, small doughing machines, mechanically or electrically controlled refrigerators, are but examples. Possibly one of the most interesting developments has been in the installation of mechanical washing machines for plates, dishes, cups, knives, etc. The number of pieces of china and cutlery is perhaps not appreciated. The modest two‐course lunch means that twelve articles, all of different sizes, shapes or materials of construction, must be washed; the seven‐course dinner requires 30–40 articles. The organisation to provide these articles in a steady stream sufficient for the needs of some hundreds of customers in the course of an hour or so must be very complicated, and one of the important cogs in the machine is “ washing up.” In the domestic scullery, unless particular precautions are taken, hot, hard water and soap are taken, and, by their admixture, produce a shiny scum which is mixed up with the soapy water. This scum and the water itself become loaded with grease during the washing process and the china is removed, carrying on its surface dirty, greasy, soapy water with its complement of soap scum. These are then wiped off with a drying cloth clean at first, but becoming gradually impregnated with grease, soap and scum, with the result that the surface of the china is finally covered with a thin transparent film of these objectionable substances. If the china, after removal from the wash‐bowl and when still wetted with grease‐laden soapy water, were rinsed under the hot tap until all this wash water were removed and replaced by clean hot water, and the china were then allowed to dry of its own accord, it would be chemically free from grease and would require no polishing. It would, moreover, not have to be handled at all. The essential factors of mechanical washing are therefore : (1) A detergent treatment that will emulsify all greasy substances and dislodge adherent food debris. Soap and suitable alkalis are used in this treatment. (2) A rinse treatment using clean hot water that will remove all detergent water from the china. (3) A drying treatment that is spontaneous and is carried out without touching the articles. Thus the production of washed articles entails a machine washer supplied with hot, softened water and suitable detergents; controls of rate of water supply, temperature, injection of detergent and rate of movement of china through the machine are of course all automatic. Treatment is generally in four stages—first a detergent treatment by high pressure jets, then a first and a second rinse treatment again by pressure jets, and finally a last rinse treatment provided by the incoming clean, hot, softened water taken directly from supply. The clean china is now so hot that within a few seconds of its emergence from the machine it is dry. It is then ready for use. It is only within the last century that “ gastronomy ” has been popularised, for the bulk of the population is now catered for with more care than ever before. The presentation of meals has advanced enormously, and the palatability of food has been studied with far more concern than ever before. Palatability, the controlling factor in eating, is a complicated attribute, and includes all those factors which can be considered as appealing to the senses. Sensation‐producing qualiites are odour, flavour, texture, temperature and appearance, appearance including form, design, size and colour. Palatability is no sure guide to food selection—“ Eat what you like and you need have no further concern about your food ”—modern scientific thought has demonstrated the fallacy of such a statement; nevertheless there are more factors of importance than the “ completeness ” of a food. To be informed that a mass of food contained all the necessary factors for proper nutrition has no effect on the gastric secretions, but the odour of a frying steak may make the mouth water : a badly baked meat pic, no matter how nutritious, lacks the appeal of one with the colour properly developed. This catering for masses of people has raised a number of important questions which the chemist has answered in many cases. As in the case of chain‐stores, where the public expects to get the same goods at the same price, be they purchasing in Manchester or Sidmouth, so in the case of chain‐restaurants the public demand the same standard of goods wherever they may happen to be eating. The consequence of this is that the cooking of a potato, the roasting of a joint, the frying of a fillet of fish, the production of a poached egg on toast, have to be standardised, and the chemist has collaborated with the engineer to produce the plant and machinery which will ensure, within reasonable limits, that the public be satisfied in so far as this consideration is concerned. Only a scientist can answer such questions as : for how many hours and under what conditions may a tin of sardines be kept after opening? What is the “ life ” of a meat pic in summer and what in winter? How long can Russian salad prepared under standard conditions be kept? What are the best conditions for the preparation and keeping hot of boiled cabbage : Incidentally the scientist has been forced to give attention to many problems outside the realm proper of food : for example, the standardisation of the crockery and glasses to reduce breakage to a minimum, the question of the colours to be used for the plates and cups and saucers, so that fading by the chemical treatment or by mechanical abrasion in washing or in general use be brought to a minimum. The solution of problems of the service of food in restaurants is not perhaps a spectacular field of work for the scientist, but, in view of the millions of meals served daily in England, its importance can hardly be over‐estimated. Such are some of the impacts of Science on Food. The sketch is naturally incomplete and many aspects have not been mentioned at all. The application of new scientific knowledge to food problems is continually assuming greater importance in the feeding of the people. This does not imply that science is supplanting the art of the chef; it may modify, perhaps simplify, the processes concerned with the preparation of food, but its main function is to interpret the principles on which the art is founded, and to adapt the accumulated knowledge to modern conditions.

In this special feature details are given of those British paints which can be described as corrosion‐resistant primers, both one‐ and two‐pack. The materials are generally classified according to the base or pigment which actively prevents corrosion—e.g. metallic zinc in zinc/epoxy formulations— or by the base which produces a barrier action against corrosion, e.g. bitumen in bituminous paints. Exceptions to this are the etching primers, which are separately classified. About 300 primers are described, the manufacturers' names and addresses being cross‐indexed and listed separately on page 48.

DRAWING of metals occurs in innumerable ways, both hot and cold. Here, however, we are concerned only with the cold drawing operations used to form vast tonnages of steel, and large quantities of non‐ferrous metals, as tube and wire, and for the forming of sheet metals (especially by deep drawing).

In this second part of the article we learn something more of the conditions in which corrosion of galvanizing can or cannot flourish and of the measures necessary for its prevention. Statistics are listed of experimental work on the life of hot‐dip galvanized coatings and related to different atmospheres.

The amount of gas blowing into the molten solder in plated‐through‐holes during wave soldering is dependent upon the moisture content of the board and the strength of the copper barrels to withstand the pressure of gas. This strength is dependent, in turn, upon both the thickness of the copper electroplate and the quality of the original electroless copper deposit. The problem of blowholing may be overcome by improving the copper quality and/or by baking the PCB prior to soldering. This paper gives a scientific framework linking the important parameters involved in the control of blowholing. Full data are given to enable the allowable moisture content of a PCB to be calculated in respect of the pressure generated during soldering and of the strength of the copper barrels. If baking is required to attain the required low moisture levels, then certain data are required to quantify the effects of the storage times and the environment conditions between that bake and the subsequent soldering. These data are given.

By hot‐dip galvanizing steel and iron objects and constructions the corrosion resistance obtained is already very high and in the majority of cases no paint system is required as a supplementary protective coating. In practice, however, six cases can be shown where it is necessary or desirable to paint hot‐dip galvanized steel.

SMT stencil cleaning has traditionally been thought of as a ‘maintenance’ procedure with little or no impact on production. Today, CFC and VOC cleaning processes are being replaced because of environmental concerns, and fine‐pitch and ultra fine‐pitch assemblies are commonplace. These changes in cleaning processes and product specifications have shed new light on the importance of properly cleaning SMT screens and stencils in order to prevent damage to the stencil and potential production‐related problems.This paper takes an unbiased look at the different stencil cleaning processes available through the eyes of an SMT stencil manufacturer. The paper outlines the advantages and disadvantages of using ‘jet spray’ washersvs ‘ultrasonic’ washers, aqueous and semi‐aqueous vssolvent cleaning agents, and the effects of hot wash solutions and hot drying air vsambient wash solutions and drying techniques.Specific criteria evaluated include: cleaning effectiveness of the process; potential adverse effects of the process on the integrity of the stencil; production down‐time and other potential production‐related problems; potential health hazards to users; environmental impact of the process, and waste stream management.Magnified photography is used to demonstrate the relative effectiveness of various cleaning technologies. Third party references of other industry experts, along with the author's own experiences, are cited to support the information provided.

The purpose of this paper is to evaluate the effect of nitrogen and air atmospheres on the solderability testing of plasma‐treated hot air solder level (HASL) finish printed circuit boards (PCBs).

In this paper, the soldering performance of plasma‐treated HASL finish PCBs in nitrogen and air atmospheres have been evaluated using the wetting balance technique. The results were compared with the performance of conventionally flux‐treated samples soldered in air and nitrogen atmospheres and non‐flux treated samples soldered in air. Auger chemical analysis results were also compared with the solderability test results in order to obtain a complete profile of the plasma‐treated and non‐treated surfaces.

The results of the auger chemical analysis show high organic (carbon) levels in the control samples and a significant drop in organic levels in the plasma‐treated samples. The significant drop in the level of carbon leads to a decrease in contact angle and an increase in both surface energy and solder wettability. The results indicate that plasma cleaning of PCBs prior to soldering is a viable alternative to the conventional use of flux.

The paper indicates that the soldering performance of plasma‐treated PCBs in air and nitrogen atmosphere are comparable. The findings give the motivation for the use of plasma‐assisted dry cleaning for fluxless soldering.