C-Enhancements, Processes and Finishes Flashcards
1
Q
Polymer additives-Lubricants?
A
-The addition of wax reduces the viscosity of the molten polymer.
-It allows more intricate shapes to be formed or allows the moulding temperature to be lowered, which saves energy.
2
Q
Polymer additives-Thermal antioxidants?
A
-They prevent the polymer oxidising or discolouring due to excessive heat during processing.
3
Q
Polymer additives-Pigments?
A
-Tiny particles mixed into the polymer in its molten state to give colour to the final product.
4
Q
Polymer additives-Antistatics?
A
-Plastics are used to insulate products but it can lead to a build-up of static electricity, which attracts dirt and dust.
-Antistatics improve surface conductivity by attracting moisture, therefore reducing the static charge.
5
Q
Polymer additives-Flame retardants?
A
-When added to polymers it reduces the likelihood of combustion or the spread of fire.
6
Q
Polymer additives-Plasticisers?
A
-They are added to allow plastics to become less hard and brittle.
-Added to food wrap to allow it to be stretched over food.
7
Q
Polymer additives-Fillers?
A
-They provide bulk to the product meaning that less polymer is required and improve the polymer’s properties.
8
Q
Polymer additives-Antioxidants?
A
-Helps to reduce the deterioration of a polymer from exposure to oxygen in the air.
9
Q
Polymer additives-UV light stabilisers?
A
-Prevent polymer chains from being broken down by sunlight.
10
Q
Polymer additives-Biodegradable plasticisers?
A
-They make the polymer more flexible, softer, and easier to break down, which can lead to a faster degradation time.
11
Q
Polymer additives-Bio-Batch additives?
A
-Oxy/Photo/Hydro-degradable additives can be added to polymers to help reduce degradation times.
12
Q
Metal enhancements-Work hardening?
A
-Bending, rolling, or hammering the crystals within a metal are distorted, leading to improved tensile strength and hardness.
-The crystals are prevented from moving freely, which can result in less ductility.
13
Q
Metal enhancements-Annealing?
A
-Used to make a work-hardened metal easier to work with by making it less brittle and more ductile.
-The metal is heated and then very slowly cooled allowing the metal crystals to grow and then move back into place.
14
Q
Metal enhancements-Case hardening?
A
-Creates a surface with a greater hardness and more resistance, while the inner core retains its softer properties.
-Stage 1:Carburising, it changes the chemical composition of the surface by increasing the surfaces carbon contant.
-Stage 2:Quenching, the hot metal is quenched in water, which seals the hard surface case.
15
Q
Metal enhancements-Hardening?
A
-Medium/High carbon steel are heated and then held at this temperature for a given time then quenching it.
-It will alter the crystalline structure, which greatly increases the hardness but also the brittleness.
16
Q
Metal enhancements-Tempering?
A
-It is carried out after hardening to reduce the excessive hardness and increase the toughness.
-It is heated below the critical point and then cooled, the rise in temperature causes a reduction in hardness.
17
Q
Wood enhancements-Resins?
A
Manufactured boards use resins to produce boards that are not affected by temperature and humidity as much as solid woods. Also, have uniform strength with none of the grain problems seen with solid woods.
18
Q
Wood enhancements-Laminations?
A
Veneers are laminated onto the surface of cheaper woods to enhance the properties.
19
Q
Wood enhancements-Preservatives?
A
Used to protect the wood from insect and fungal attacks, they penetrate the timber to give it enhanced properties.
20
Q
Wood enhancements-Pigments?
A
Give different coloured shades to enhance the aesthetics of the wood products.
21
Q
Wood enhancements-Modified natural polysaccharides?
A
They effectively cure within the wood to give it increased toughness and hardness.
22
Q
Wood enhancements-Structural composite lumber and Laminated veneer lumber?
A
Engineered woods made by layering veneers or strands of woods with resins and then heat is used to cure them. They are less prone to defects like warping, splitting or shrinking.
23
Q
Polymer processes-Vacuum forming?
A
-The mould, with a draft angle. is placed on the bed of the machine, which is called the platen. The platen is lowered to the bottom of the machine.
-Polymer sheet is clamped over the mould and heated.
When the polymer has softened, the platen is raised into the polymer and the heat is removed.
-The vacuum is switched on, which sucks the polymer onto the mould.
-Once the polymer has cooled and returned to a solidified state, the platen is lowered and the vacuum is switched off.
-The mould is removed and any excess polymer is trimmed off.
24
Q
Polymer processes-Thermoforming?
A
-It is similar to vacuum forming except there is an additional mould applied at the same time as the vacuum.
-The two moulds trap the softened polymer in between them, giving extra detail to the moulding.
-Used for fine details such as embossed logos and lettering.
25
Polymer processes-Calendering?
-Used to make thin polymer sheets and films.
-Works by heating pellets of thermoplastics, which are then extruded being a series of heated rolllers to make it thinner.
-It is then finished on cooling rollers before being cut into into standard stock sheet sizes.
26
Polymer processes-Line bending?
-Uses an electrical heated element that provides heat along a line, in order to produce bends in sheets of thermoplastics.
-Typically used to make products such as boxes.
-It is labour intensive and quite slow.
27
Polymer processes-Lamination (lay-up)?
-The mould is coated with a release agent or covered with parcel tape.
-A top layer of gel coat is applied.
-Fibreglass matting is laid over the former, then a polyester resin is brushed onto the matting and a small roller is used to push out any air bubbles and smooth out the matting.
-This is repeated until the desired thickness is achieved.
-The GRP is then allowed to set before being removed from the mould.
28
Polymer processes-Injection moulding?
-Thermoplastic granules are poured into a hopper.
-A screw thread is rotated, which pulls the granules through the chamber and past heaters.
-When the polymer has melted, a hydraulic ram forces the screw thread forward, which injects the polymer into the mould.
-The mould is water-cooled, which enables the polymer to harden quicker.
-The mould opens and ejector pins push the moulding out.
-Any excess polymer is trimmed.
29
Polymer processes-Blow moulding?
-The polymer is fed into a hopper.
-A screw pulls the polymer through a heated section, melting the polymer.
-The melted polymer is extruded as a tube, which is called a parison.
-The mould sides close around the parison and air is injected into the mould, forcing the polymer to the sides.
-The polymer is allowed to cool, then the mould opens and the finished bottle is ejected.
30
Polymer processes-Rotational moulding?
-Polymer powder or granules are loaded into a mould, which is clamped and sealed.
-The mould is transferred to an oven and heated.
-The mould is rotated around two axes and the polymer is coated around the inside of the mould.
-Once the polymer is at the correct thickness, the mould is cooled.
-When the polymer has solidified the part will shrink slightly allowing it to be removed from the mould.
31
Polymer processes-Extrusion?
-Polymer granules are poured into a hopper.
-The screw moves the polymer granules past heaters, which softens the polymers.
-When sufficient polymer has melted a hydraulic ram pushes the screw, forcing the polymer through a steel die.
-The extrusion may be supported by rollers as it leaves the die and is cooled by water or air.
-The extrusion is then cut to the desired length.
32
Polymer processes-Compression moulding?
-A thermoset polymer is inserted between the two halves of a preheated mould.
-The moulds are closed and a hydraulic press is applied. The pressure ensures that the polymer takes the shape of the mould.
-When the moulding has cured, the machine opens and the polymer is removed.
-Excess polymer known as flash is removed.
33
Metal processes-Press forming?
-Sheet metal is clamped over a die of the product.
-A hydraulic press pushes the die into the sheet metal, cutting blades may be used to punch holes or trim excess material.
-The die is lowered and the pressed sheet component is removed.
-The sheet may be placed into further press forming machines for more complex shapes.
34
Metal processes-Spinning?
-A former called a mandrel is put into a chuck and the sheet metal is held in place between the mandrel and the tail stock.
-The roller tool is moved into the sheet and is rotated with the mandrel.
-The metal will start to stretch the metal over the mandrel.
-The roller is moved along the mandrel maintaining constant pressure.
-The roller is moved to the end of the mandrel in order to finish the shape of the product.
-The finished product is removed from the mandrel and any excess material is removed.
35
Metal processes-Cupping and deep drawing?
-The pressing blank is clamped over a deep drawing die.
-A hydraulic press moves the deep drawing punch to be in contact with the blank, it then pushes the blank into the die cavity making a cup shape.
-The cup is then forced further down to make the desired tube shape.
36
Metal processes-Drop forging?
-A die is secured to the top of an anvil.
-A ram is also equipped with a die that resembles a mould.
-The billet is heated above its recrystallisation state, which prevents the product from work hardening.
-The heated billet is placed into the anvil die and the hydraulic ram is brought down with a force.
-The ram is lifted and the final product removed.
37
Metal processes-Wrought iron forging?
-Wrought iron is heated in a forge.
-It is then held with tongs and hammered over an anvil until the desired shape is reached.
38
Metal processes-Bending?
-Clamping the stock metal between a complementary punch and die.
-The punch is forced into the metal in order to bend it.
39
Metal processes-Rolling?
-A stock metal is passed through a set of rollers to reduce the thickness.
-Can be hot rolled, will have uniform properties throughout and no faults but the surface can be coated with carbon deposits.
-Can be cold rolled, no carbon deposits will form and therefore a tighter tolerance.
40
Metal processes-Sand casting?
1) A pattern is made of the item being cast and then sand is packed around it.
2) A second box is clamped on top with the top half of the pattern and wooden stakes are added to create the sprues.
3) Sand is again packed into the second box.
4) The boxes are separated and the pattern and stakes are removed and then the boxes are clamped back together.
5) Molten metal is poured into the sprue and when the cavity is full it flows up the riser to indicate it is full.
6) Once it is cooled the sand is removed and the runners and risers are cut off with a hack saw.
-It is slow and labour intensive as the moulds are single use so is only used for one-off batch production.
-It does not give a very high quality finish.
41
Metal processes-Die casting?
-Uses complex and costly moulds making it only suitable for large batch and mass production.
-It provides a high quality surface finish.
-Gravity die casting, as in sand casting the metal flows down the runner and up the riser filling the mould and once it has cooled the mould is opened.
-Pressure die casting casts items quickly and in high volumes:
*Hot chamber, the molten metal is force into the mould under high pressure to fill the mould, which allows fine details to be moulded.
*Cold chamber, the molten metal is heated sperately and then ladled into the chamber where the ram forces it into the mould.
42
Metal processes-Investment casting?
-Used to cast intricate or awkward shapes.
1) A pattern of the product is made using wax.
2) The pattern is dip coated with clay and then fired to make it hard, the wax is then burned away leaving a hollow mould.
3) Molten metal is poured into the clay mould.
4) Once it has cooled the clay is then broken away.
43
Addition and Fabrication processes-MIG welding?
-An electrical arc creates heat which melts the joint area.
-A wire electrode of the same material being joined also melts into the arc and fills the gap between the two pieces.
-The operator swirls the welding gun as they move over the joint to form a continuous bead of weld.
-The electrode wire is stored on a reel and advances through the welding gun as the trigger is pressed (One handed).
-An inert gas forms a flux sheild, the gas replaces the oxygen to prevent oxidation at the joint.
44
Addition and Fabrication processes-TIG welding?
-Similar to MIG welding but the tungsten electrode does not melt and instead a separate filler rod is used (Two-handed).
-The processor allows for greater control and a more accurate and stronger weld but it requires a high skill level and is quite slow.
45
Addition and Fabrication processes-Oxy-acetylene welding?
-Uses a mixture of high pressure gases to form an intense flame.
1) The metal is prepared by grinding an angle on the edge to create a V shape when the pieces are joined.
2) The joint is heated and a steel filler rod is introduced into the area to form the seam.
46
Addition and Fabrication processes-Brazing?
-Uses lower temperature and the resulting joint is not as strong as welding.
1) The material to be joined is cleaned and degreased.
2) The two pieces are clamped together.
3) A flux is applied to prevent oxidising.
4) The joint is heated and a brazing rod is applied to the area.
5) It will flow along the joint to the hottest area, so can be made to follow the joint by manipulating the torch.
47
Addition and Fabrication processes-Soldering?
-Can only be used for lightweight applications.
-The metals should be clean and no gaps between the areas being joined.
-It uses a filler material with a lower melting point.
1) The metal is cleaned and degreased.
2) The joint area is wired up or clamped.
3) The metal is heated up to the melting point of the solder.
4) The solder is added to the metal causing it to flow along the joint by capillary action.
5) The metal is cleaned to remove any flux residue.
48
Addition and Fabrication processes-Riveting?
-A permanent joining method used to join sheet metal or plates.
-The head of the rivet is domed shaped and the shaft is hammered over to squeeze the two pieces together.
49
Addition and Fabrication processes-Pop riveting?
-The rivet head is pushed through a hole drilled through the two pieces being joined.
-Riveting pliers grip and pull the pin, this causes the head of the rivet to be squashed and pulls the two pieces together.
-The pin breaks and is disposed of.
-It is ideal when the underside of the joint is not exposed.
50
Temporary Fasteners and Joining methods-Self-tapping screws?
-A pilot hole is drilled through the pieces being drilled.
-When it is screwed into the pilot hole it cuts its own thread.
-Can be used where forming a screw head good increase the cost of the product. (Injection moulding)
51
Wasting processes-Milling?
-Similar to a drill but can move left and right and forwards and backwards as well as up and down, so the workpiece can be machined in a range of directions.
-Can be done manually or using a computer controlled machine.
52
Wasting processes-Turning?
-A process carried out on a lathe.
-The workpiece is held in a rotating chuck and machined to reduce the diameter to the desired dimensions.
53
Wasting processes-Flame cutting?
-A torch delivers a very intense and focused flame to cut low carbon and alloy steel plates.
-The metal is heated and a melt pool forms, then a jet of oxygen is introduced to intensify the flame and piece the material.
54
Wasting processes-Plasma cutting?
-It uses a conductive gas to transfer energy to the conductive material to create a fast clean cut.
55
Wasting processes-Laser cutting?
-A wasting process that uses a CAD file to direct a laser.
-A high powered laser melts the material and a high-pressure gas/compressed air blows the melted material away.
-Produces a fine cut with a high quality surface finish, there is little warping or distortion to the material.
-The laser is very accurate and uses less energy then other processes.
56
Wasting processes-Punching and Stamping?
-CNC machines stamp out sections of sheet material using hardened punches.
57
Wood processes-Butt Joint?
-The simplest method of joining two pieces of timber.
-It relies upon adhesives to make the bond, it is clamped and allowed to dry.
-It is only suitable for lightweight applications such as modelling.
58
Wood processes-Dowel joint?
-Glue is put into the holes and the dowels are hammered into position and the two halves are clamped together.
-Is a simple joining method but stronger than a butt joint.
-Typically used in flat pack furniture along with another knock down fitting.
59
Wood processes-Mitre joint?
-Similar to a butt joint but the ends are cut to 45 degrees each and are then glued and clamped together.
60
Wood processes-Comb joint?
-Two pieces are joined by interlocking, the comb also creates an increased gluing surface area.
-The increased surface area creates a strong joint great for creating boxes
61
Wood processes-Dovetail joint?
-Perfect for making drawers as this joint creates directional strength.
-Once they are glued together they are impossible to pull apart.
62
Wood processes-Mortise and Tenon joint?
-A square/rectangular hole (Mortise) is cut and then glue is spread inside.
-A complementary-shaped tenon is cut and the two pieces are clamped together.
63
Wood processes-Housing joint?
-Is useful for making cabinets and shelving.
-A groove is cut across one piece and the end of the second piece is slotted into it.
-It can be glued or not to allow it to be adjusted but it is structurally strong either way.
64
Wood processes-Half lap joint?
-Made by cutting a step into the end of each piece.
-It is simple but is stronger than a but joint because there is an increased surface area.
65
Wood processes-Modesty blocks?
-Small rigid polymer blocks, which have moulded holes that take screws to join to panels together.
-They very simple to use but are not particularly strong and are unattractive.
66
Wood processes-Cam-lock connector?
-A metal dowel is screwed into one of the pieces and the cam is a disk that fits into a pre-drilled hole on the other piece.
-The dowel slots into the disk and then the cam is rotated with a screwdriver to lock them together and pull the pieces tighter.
67
Wasting processes-Turning?
-Machining wood on a lathe.
-Turning between two centres (Table legs), used to reduce the diameter.
-Turning on a face plate, is used to machine domes and bowls, a thick piece of timber is screwed at its base to the face plate.
-Turning using a chuck, used to grip the item when it is machined, used when the end of the spindle needs to be drilled but can also be used for bowls and vases.
68
Wasting processes-Routing timber?
-Used to make slots, holes, or decorative mouldings on timber.
-Can be handheld and used with guides/jigs in order to produce continuous grooves along the length of the timber.
-Can be CNC, where CAD drawings are downloaded to the routers and converted into a path for the router to follow.
69
Forming processes-Milling timber?
-They run slowly and great for machining timber accurately so used for small, basic jobs.
-They do not have the same range of movement as CNC router but can still be operated with a computer or manually.
70
Wasting processes-Lamination?
-The process of bonding to materials together, typically wood with veneers.
-The materials can be glued together and bent over a former, so that when they dry they will form the shape of the former.
-While drying they can just be clamped together or put in a vacuum bag where the pressure will pull the laminates together to ensure that there are no gaps in the laminating.
71
Forming processes-Steam bending?
-Heat and steam will make timber strips pliable enough to be shaped over a former.
-It is then clamped to the former until it dries.
-It has advantages over laminating because it is quicker than waiting for layers of glue to dry, and it is less wasteful as laminated parts often require trimming.
72
Adhesive and fixings-Polyvinyl acetate?
-A common use to bond most woods as it soaks into the surface and once the water content is absorbed then it will set.
-It is widely used for indoor construction as it is not a waterproof adhesive.
73
Adhesive and fixings-Contact adhesives?
-It is used for large areas like sheet material either of the same or different material.
-The two surfaces are coated in the contact adhesive and left for 10 mins, the adhesion is instant, which means that clamping is not required.
74
Adhesive and fixings-UV hardening adhesives?
-It is a clear liquid that cures to form a bond when exposed to UV light, used on glass and polymers.
-The advantages are that any excess can be easily wiped away before it is cured, it has a fast curing time and is transparent so good for use on glass.
75
Adhesive and fixings-Solvent cement?
-A clear liquid used to join polymers, it works by softening the surface of the polymers allowing them to be fused together.
76
Adhesive and fixings-Jigs and Fixtures?
-A fixture hold your work in place whilst a manufacturing process takes place.
-A jig both holds your work in place and guide the tool.
-They are used to ensure repeatability and accuracy, for example for drilling parts where the screw need to be in the same place every time.
77
Adhesive and fixings-Router jigs?
-Used to help shape the timber accurately and consistently.
-They can be used to either angle the router in the fixed position or guide it along a piece of work.
78
Adhesive and fixings-Sanding jigs?
-Hold and guide timber whilst it is sanded and using a jig will ensure that it is an accurate and consistent angle.
79
Paper and Board Finishing-Laminating?
Lamination via encapsulation-The paper is fed through the laminator and heat sealed leaving a polymer sheet cover on both sides.
-Lamination via surface coating-
80
Paper and Board Finishing-Embossing?
-Creates a raised design on the surface to give a visual and tactile effect without the need of additional printing.
-It uses two dies, the substrate sheet is placed between them and held under pressure until the embossed area is formed.
81
Paper and Board Finishing-Debossing?
-The opposite of embossing, the image sits below the surface of the paper or card.
-The products using this are also produced in the same way between two dies.
82
Paper and Board Finishing-Foil blocking?
-Heat and pressure are used to create depth and texture in areas to improve the aesthetics.
-The metallic foil adds contrast to the card.
-Used to enhance business cards.
-Similar to embossing but the design is stamped onto the material through the foil, which is then transferred to the card.
83
Paper and Board Finishing-Varnishing, UV varnishing, and spot varnishing?
-Varnishing is used to enhance the colour as well as some protection against dirt and water. It is only suitable on precoated paper as these will not soak up the varnish.
-UV varnishing, provides a very smooth finish, the varnish is applied and then cured using a UV light, it provides a high-quality finish that is abrasion and chemical resistance.
-Spot varnishing, is similar to the other types of varnishing but is only applied to specific areas
84
Paper and Board Printing Processes-Screen printing?
-Used for simple and effective printing on small print runs, it can be achieved with minimal set up costs due the basic equipment.
-The image to be printed is created on a screen (a mesh held by a frame), it has open areas to allow the ink to pass through.
-A different screen is required for each new colour, which can increase the time taken to print and the production costs.
-A squeegee is then used to force the ink through the mesh onto the substrate.
85
Paper and Board Printing Processes-Flexographic printing?
-It uses a four colour process (CMYK), where each colour is printed on top of each other in various quantities to create the print colour required.
-To ensure an accurate and non-blurry print the colours need to line up precisely with each other.
-It is the least expensive printing process due to the fast drying water based inks and uses rolls rather than sheets so it allows large continuous prints.
-Advantages: high print speed, ideal for long print runs, prints on a wide variety of substrate materials, low cost per print and low maintenance.
-Disadvantages: Printing plates are expensive but last for millions of prints, takes a large amount of substrate, excess material may be wasted and it is time consuming to change for any alterations to the print.
86
Paper and Board Printing Processes-Offset lithographic printing?
1) The printing substrate is either sheet or roll-fed into the printing machinery.
2) Printing plates are produced by a laser, which etches the image onto the plate.
3) The ink is applied to the printing plate, and the cylinder rotates onto a blanket roller which becomes coated with ink.
4) As the substrate is fed through, the image on the blanket is transferred to the substrate to produce the printing.
-Advantages: Consistently high image quality, suited to higher volume print runs, quick and easy production of printing plates and the printing plates last a long time.
-Disadvantages: Expensive set up and running costs for small quantities.
87
Paper and Board Printing Processes-Digital printing?
-Produce full colour, highly detailed prints both front and reverse side quickly and efficiently.
-The ink sits on top of the paper and is allowed to dry.
-It can be used for high or low volume print runs.
88
Polymer finishing-Adding colour?
-Pigments are added to create a particular colour, either during manufacturing process or during the production of the stock form.
89
Polymer finishing-Acrylic spray paints?
-Polymers are self finishing but additional finishes can be added to enhance the aesthetics.
-Acrylic paint is fast drying, can be water resistant and can protect against the effects of UV light and weathering.
90
Polymer finishing-Overmouldings?
-Moulding a second polymer over parts of a product to primarily provide areas of grip or texture, or to highlight different different colours for different components.
91
Metal finishing-Cellulose and acrylic paints?
-Paints can provide colour and texture to finish paints, whilst also providing a protection against corrosion.
-The surface of the metal should be cleaned prior to application, so that the primer coat has a sound surface to grip.
92
Metal finishing-Electroplating?
-Involves using a metal to coat a usually cheaper base metal, to provide a protective layer and give it greater aesthetics.
-Both materials are placed into a electrolyte solution and as the direct current is applied, the product attracts the donor material.
93
Metal finishing-Polymer dip coating?
-The metal product is heated to 230 degrees, then the hot component is dipped into a tank of fine polymer powder which has air blowing through it.
-The retained heat allows the polymer powder to melt over the product and then it is air cooled.
94
Metal finishing-Metal dip coating?
-The metal product is dipped into a tank of the molten plating metal to provide a barrier against corrosion.
-The metal must be cleaned and degreased before the metal plating.
-Zinc plating (Galvanising), the metal is dipped into molten zinc.
95
Metal finishing-Powder coating?
-The product is statically charged and a thermoset polymer resin is sprayed on.
-It causes a strong attraction between the powder and the product, the product is then baked in an oven where the heat melts the powder to give an even coating.
-It is more hardwearing than paint.
96
Metal finishing-Varnishing?
-Provides a clear finish to a product to protect the metal and allow the colour of the base metal to show through.
-Primarily used on metals with already good aesthetic properties.
-The metal should be polished to a shine and any surface grease removed, so that the varnish can be applied by spray or with a fine brush.
97
Metal finishing-Sealants?
-They are tough, polymer based sealant coatings that protect polished surfaces from decay or tarnishing.
-It is generally applied with a cloth to produce a film that is allowed to cure for 15 mins and then buffed with a cloth to a shine.
98
Metal finishing-Preservatives?
-Provide temporary in-process or medium to long term post processing protection.
-Often used on mould and dies to prevent fingerprinting, minor atmospheric corrosion or condensation build up.
-They can be applied by wiping on with a cloth, spray or immersion.
99
Metal finishing-Anodising?
-Commonly used on aluminum as it enhances the natural oxide layer, giving it increased hardness and toughness.
-Can also provide a colour to the product.
-An electrical current flows from the part to be treated to the negative cathode causing the oxide layer to build up evenly on the treated parts surface.
-Can also be finished with a clear varnish to provide further protection.
100
Metal finishing-Cathodic protection?
-Is a method used to control the rate of corrosion by making the metal the cathode of an electrochemical cell and the anode a sacrificial metal which is more easily corroded.
-It means that the anode corrodes, whilst the base metal is protected.
-Its main use is to protect steel structures buried in soil or immersed in water.
1) Impressed current: the component to be protected is connected to a power supply. The impressed direct current flows from an inert electrode through a liquid to the component being protected.
2) Sacrificial anode: A more electrochemically active metal is wrapped around the joint to provide resistance to corrosion. It is monitored for signs of corrosion and replaced when the base metal is no longer protected.
