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Electropanting (penyaduran)

Electroplating is a process that uses electrical current to reduce dissolved

metal cations so that they form a coherent metal coating on an electrode. The term is

also used for electrical oxidation of  anions onto a solid subtrate, as in the formation

silver chloride on silver wire to make silver/silver-chloride electrodes. Electroplating isprimarily used to change the surface properties of an object (e.g. abrasion and wear 

resistance, corrosion protection,lubricity, aesthetic qualities, etc.), but may also be

used to build up thickness on undersized parts or to form objects by electroforming. 

The process used in electroplating is called electrodeposition. It is analogous to

a galvanic cell acting in reverse. The part to be plated is the cathodeof the circuit. In

one technique, the anode is made of the metal to be plated on the part. Both

components are immersed in a solution called anelectrolyte containing one or more

dissolved metal salts as well as other  ions that permit the flow of electricity. A power 

supply supplies a direct currentto the anode, oxidizing the metal atoms that comprise

it and allowing them to dissolve in the solution. At the cathode, the dissolved metalions in the electrolyte solution are reduced at the interface between the solution and

the cathode, such that they "plate out" onto the cathode. The rate at which the anode

is dissolved is equal to the rate at which the cathode is plated, vis-a-vis the current

flowing through the circuit. In this manner, the ions in the electrolyte bath are

continuously replenished by the anode.[1] 

Other electroplating processes may use a non-consumable anode such as lead or 

carbon. In these techniques, ions of the metal to be plated must be periodically

replenished in the bath as they are drawn out of the solution.[2] The most common

form of electroplating is used for creating coins such as pennies, which are

small zinc plates covered in a layer of  copper  [3] 

Electroplating changes the chemical, physical, and mechanical properties of the

workpiece. An example of a chemical change is when nickel plating improves

corrosion resistance. An example of a physical change is a change in the outward

appearance. An example of a mechanical change is a change in tensile strength or 

surface hardness which is a required attribute in tooling industry.[5] 

Electroplating is a useful process. It is widely used in industry for coating metal

objects with a thin layer of a different metal. The layer of metal deposited has some

desired property, which metal of the object lacks. For example chromium plating is

done on many objects such as car parts, bath taps, kitchen gas burners, wheel rims

and many others.

Pengekstrakan logam (Extract ion of metal )

Metals are often extracted from the Earth by means of mining, resulting in ores that

are relatively rich sources of the requisite elements. Ore is locatedby prospecting techniques, followed by the exploration and examination of deposits.

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Mineral sources are generally divided into surface mines, which are mined by

excavation using heavy equipment, and subsurface mines. 

Once the ore is mined, the metals must be extracted, usually by chemical or 

electrolytic reduction. Pyrometallurgy uses high temperatures to convert ore into raw

metals, while hydrometallurgyemploys aqueous chemistry for the same purpose. The

methods used depend on the metal and their contaminants.

When a metal ore is an ionic compound of that metal and a non-metal, the ore must

usually be smelted — heated with a reducing agent — to extract the pure metal.

Many common metals, such as iron, are smelted using carbon as a reducing agent.

Some metals, such as aluminium and sodium, have no commercially practical

reducing agent, and are extracted using electrolysis instead.[8][9] 

Sulfide ores are not reduced directly to the metal but are roasted in air to convert

them to oxides.

Penulenan logam (Puri f icat ion metal )

In most cases, metals and their ores occur in the ground as part of complex mixturesthat also contain rocks, sand, clay, silt and other impurities. The first step inproducing the metal for commercial use, therefore, is to separate the ore from wastematerials with which it occurs. The term ore is used to describe a compound of ametal that contains enough of that metal to make it economically practical to extractthe metal from the compound.

A steel worker sampling the quality of "hot steel" duringproduction. Photograph by John Olson. Stock Market. Reproduced by permission. 

One example of the way in which an ore can be purified is the froth flotation methodused with ores of copper, zinc, and some other metals. In this method, impure oretaken from the ground is first ground into a powder and then mixed with water and afrothing agent such as pine oil. Then a stream of air is blown through the mixture,causing it to bubble and froth. In the frothing process, impurities such as sand androck are wetted by the water and sink to the bottom of the container. The metal oredoes not adsorb water but does adsorb the pine oil. The oil-coated ore floats to the

top of the mixture, where it can be skimmed off.

Penyediaan bahan kimia (Manufacture of chemicals )

There has been a rapid growth in the development of the chemicals that are used for various

industrial applications in the last few decades. These chemical products are used for 

different purposes like engine fuels, paints and dyes, cosmetics, soaps, insulators,

detergents and so on. They are also used vastly for various research purposes in military

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warfare. It is the way that these chemicals are put to use that determines whether they can

be regarded as industrial chemicals or otherwise.

Variety of industrial chemicals:

There are numerous varieties of chemicals that are being put to use for the manufacture of 

different commercial chemical products that are highly useful to man. Some of these

chemicals include:

Phosphoric acid: It is a very commonly used chemical that is necessary for the

manufacture of fertilizers and several food items like soft drinks and others.

Sulphuric Acid: This useful chemical is used for the removal of dangerous substances

and disables the effects of alkaline substances.

Chlorine: Another popular chemical used widely for the manufacture of the bleaching

agents.

Sodium carbonate: This chemical is used in large numbers for the manufacture of 

commercial chemical products like cleaning agents and glass as well.

Oxygen: This is a very necessary chemical used an oxidizer in the reaction mixtures.

Urea: A very common chemical used for the production of fertilizers and cattle feed.

Methanol: This chemical produced from carbon monoxide and hydrogen is used

mainly as a reactant for the manufacture of formaldehyde, methyl terbutyl ether 

(MTBE) and acetic acid.

Aluminium Sulphate: It is used for the treatment of waste waters in the industries and

also as a pH buffer in the paper industries.

Nitrogen: A very useful chemical that is necessary for the prevention of the

combination of Oxygen with vapor so as to avoid the risk of explosions.

Potash: This is another widely used industrial chemical that aids in the manufacture

of ceramics, glass and soaps.

Some other commonly used chemicals and their uses:

Some of the other commonly used chemicals that help in the production of various chemical

productspropylene oxide, ethylene oxide, acetone, vinyl chloride, carbon black and many

others. These industrial chemicals have really wide spread uses in numerous sectors of 

economy that include manufacturing of the consumer goods, service sectors, agriculture,

construction and so on. These chemicals have huge number of consumers spread all over 

the world who put them to a varied range of uses.

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Penyaduran plastik (Electroplat ing plastic )

Use of Plastics

Since the end of the Second World War the use of plastics has increased remarkably due

to a systematic exploitation of their principal advantages, i.e. lightness, flexibility andtoughness, ease of fabrication of complex components, and excellent surface quality as

fabricated. This has led, in a very wide range of applications, to the replacement of 

metals with plastics as materials of construction.

Applications of Electroplated Plastics

The Automotive Industry

The initial motivation for the development of processes for electroplating on to plastics

came from the automotive industry and this market sector has consistently been by far

the largest user of the product.

Once a successful process had been developed it rapidly became accepted by the

industry, and by the early 1970s large areas of nickel/chromium plated plastics trim were

appearing on vehicles. A whole range of components were produced in plated plastics,

including radiator grilles, window trim, name badges, front/rear lamp units, mirror

housings, interior trim, and auxiliary lamp units. This trend was particularly evident with

vehicles manufactured in North America, where bright trim has always been more

popular than in Europe.

The use of plated plastics in the car industry reached a peak in the late 1970s and early

1980s. After that time the use of all types of bright trim declined as the design of carschanged in order to achieve a more aerodynamic profile to improve fuel consumption.

This was particularly evident with European cars where nickel/chromium exterior trim

was almost completely eliminated except on luxury models.

This eventually produced a generation of cars that were very similar in appearance. So

by the early 1990s designers were seeking ways of creating a degree of visual

individuality and of restoring marque identity. It is perhaps ironic that one of the most

effective ways in which this has been achieved has been by restoring bright trim, albeit

within the constraints of good aerodynamic shape. This has been used particularly in high

profile areas of the vehicle such as the radiator grille.

This resurgence of application in the motor industry has produced a remarkable

expansion of the plating on plastics industry over the last three to four years. It is

estimated that in Europe as a whole the industry has grown by 50% since 1993, whilst in

the UK in particular the increase has been even more dramatic, producing a doubling of 

capacity over that period.

Domestic Fittings

After the automotive market, the next most important application for plated plastics is for

domestic fittings where the hygienic qualities of the finish and ease with which it can be

kept clean are important factors. Items commonly produced in plated plastics include

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bath and wash basin taps, sink wastes, shower fittings, bathroom accessories, and

kitchen accessories.

Other significant uses include knobs and buttons for the electronics and white goods

industry. In France in particular the production of high quality perfume bottle caps in

very large numbers represents a very important sector of the market. A new applicationappearing recently in the UK is for bar fittings and drinks dispenser units.

Penganodan (Anodiz ing ) 

 Applications

A few of the more important applications are described below, as well as newnanotechnology applications that may grow in importance.

Clear anodize 

Clear anodize usually means sulfuric acid anodize followed by hot water seal. This

is the most widely used anodize coating. It is used on some aluminum alloys as the

surface finish for automotive trim. It is also the surface for commercial

photolithography plates. The photoemulsion adheres to the anodize coating, and

the printing pattern is made by selective dissolution of emulsion. Printing ink

adheres to the emulsion and water adheres to exposed oxide. The oxide surface is

wear resistant and stands the rigors of high speed printing presses. 

Immersing the anodize coating in a dye solution before sealing creates an attractive

colored surface for consumer products.

Hard anodize 

Hard anodize is generally made by anodizing in sulfuric acid at low temperature.

This produces a coating with large cells and small diameter pores. The coating is

extremely hard and durable and is used for engineering applications such as

bearing surfaces. 

A thin phosphoric acid anodize coating is used as an adhesive bonding primer coat

on aircraft and aerospace alloy sheets. This is an excellent surface for the epoxyadhesive and also improves corrosion resistance. Chromic acid anodize is used for 

optimum corrosion resistance for severe applications, such as aerospace andmilitary use, but because chrome, in some form, is a carcinogen this process is

 being phased out.

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Architectural applications 

Architectural applications for anodized aluminum include door and window trim

and exterior structural panels. These surfaces must be stable for many years

under harsh atmospheric conditions. Neither clear nor dyed coatings are

satisfactory. Coatings ranging in color from gold to dark bronze are made by

"integral coloring" that is achieved by using certain organic acids in the anodizing

bath. The organic anions become incorporated in the oxide and cause it to darken.

Similar hues are produced by a two-step anodizing process in which

an ac anodizing follows the dc sulfuric acid step. In the ac step a metal, usually tin

or nickel, is deposited at the bottom of the pores. The metal deposit changes the

optical properties of the coating and the thickness of the metal deposit is

controlled to produce the desired color by optical interference. These coatings

have superior long term stability compared with integral colored coatings. 

Nanotechnology applications 

The importance of surface texture in the

development of pores has recently been

dramatically demonstrated, and the results open

new applications for anodized structures. A

hexagonal array of nanoscale (on the order of 

billionth of a meter) depressions was impressedon an aluminum surface using a silicon carbide die

fabricated using electron beam lithography.

Feature interval was 70-500 nm, feature depth

was 200 nm, and feature width was of similar

magnitude. This sequence is illustrated in the

sketch in Figure 8. In this particular experiment,

anodization in oxalic acid solution produced

perfectly ordered arrays of pores correspondingto the patterned texture. This is shown in Figure 9,

where the oxide on the left grew on the patterned

surface, in contrast to the oxide on the right that

grew on a surface that was not patterned.

Adjustment of process conditions produces

precisely ordered pore arrays with dimensions

suitable for use as 2-D (two-dimensional) photonic

crystals in the visible wavelength.

Fig. 8. Process for fabrication of 

ideally ordered porous oxide. Black 

structure is SiC (silicon carbide) mold 

used to make ordered array of 

convex dimples in aluminum surface

 prior to anodization (From Asoh et 

al., seeBibliography  ). 

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Pores can be used as templates to make

structures such as nanowires andnanotubes. To make nanowires the

 pores are filled with a metal, or other material,

 bycathodic deposition or  electroless

deposition. Tubes are made by coatingthe pore walls; addition of functional

groups to the tube interior wall creates

tubular nanoreactors. The wires andtubes are recovered by dissolving the

alumina (aluminum oxide) template in a

reagent that does not attack thenanostructures. Figure 10 shows

 pyrolytic carbon tubes created byflowing propylene at a temperature of 800oC (1472oF) through a porous alumina

membrane that had been separated from its metal substrate. The alumina was then

dissolved in hydrofluoric acid solution.

Rawatan sisa (Effluent treatment )

Fig. 10. Carbon tubes prepared by pyrolytic

deposition of carbon in porous aluminum oxide

(From T. Kyotani, L. Tsai, and A. Tomita, Chemistry 

of Materials, Vol. 8, p 2109, 1996).