Engneering Finishes Flashcards
(32 cards)
What is the anodising process?
Anodising is an electrolytic process for producing thick oxide coatings, usually on aluminium and its alloys. The oxide layer is typically 5 to 25ųm (micrometer) in thickness and is used to give improved surface resistance to wear and corrosion, or as a decorative layer.
Anodising Pre-Treatment
To prepare the aluminium surface for anodising, the metal needs to be cleaned. The most common process consists of three steps.
Degreasing: removing any residuals from the surface of material
Etching: involves removing die lines and other surface defects from the extrusion. Most common etching process is alkaline, after the processes the surface becomes smoother and has an even appearance.
Desmutting: removes smut and prepares the surface for the acidic anodic solution
Anodising Post-Treatment
The aluminium surface has a porous oxide structure (like a sponge), can absorb different materials to alter the surface properties. Eg. surface and be filled with glue particles to make it sticky.
Aluminium is sealed, creates highest protection of the final coating
Advantages of Anodising
- it’s easy to maintain; can be cleaned with water
- UV stable and will not peal or flake, as it is integral to the metal
- protects the base metal to offer deeper, richer metallic appearance
- enhanced natural oxide layer which increases hardness and toughness
Disadvantages of anodising
- can only use specific grades of aluminium for this process
- cannot be used on stainless steel
- can be subject to colour variations
- harder to replicate consistency between batches compared to plating.
What is Galvanising?
Is the process of applying a protective zinc coating to iron or steel, to prevent rusting. Most common method is hot dip galvanising, steel sections are submerged in a bath of molten zinc. Other methods are; electroplating
Examples
Construction
Street and outdoor furniture
Transport
Process of galvanising
Surface preparation: steel must be properly prepared prior to being immersed in a bath of molten zinc
Degreasing/caustic cleaning: hot alkali solution, mild acidic bath, or biological cleaning bath removes contaminants from the steel.
Pickling: to remove mill scale and iron oxides, steel goes through a diluted solution of heated sulphuric acid or ambient hydrochloric acid.
Advantages of galvanising
- corrosion resistance: highly resistant to corrosion, ideal for outdoor use
- durability: longer lifespan
- low maintenance: occasional cleaning
Disadvantages of galvanising
- initial cost: can be more expensive than untreated steel (aluminium)
- limited aesthetics: has a distinctive look that may not fit with all design schemes
- environmental concerns: can have environmental impacts, as it involves the sue of toxic chemicals.
Advantages of preservatives
- maintains safety and hygiene
- enables mass production
- reduces cost over time
- improves availability
- protects materials
Disadvantages of preservatives
- health concerns
- can affect taste of a food
- environmental impact
- added cost or processing
Uses of preservatives
- prevent spoilage
- extend shelf life
- maintain freshness
- enable safe storage and transport
Advantages of paints
- protection against weather and wear
- aesthetic enhancement and creative expression
- Varnishes, easy to apply and maintenance(easy to touch up and recoat)
- cost effective, versatile,
Disadvantages of paints
- environmental concerns related to the chemicals in the paint
- potential health effects from exposure and aesthetic limitations such as chipping
- can easily fade and need frequent maintenance.
Uses of paints
- decoration
- protection
- communication
Advantages of sealants
- waterproofing and air sealing
- good for bonding properties
- flexibility
- chemical and weather resistant
- can last a long time.
Disadvantages of sealants
- takes a long time to fully cure
- certain types may not bond well with specific materials
- toxic fumes
- can be expensive.
Uses of sealants
- sealing joints and gaps
- leak prevention
- thermal management
Advantages of electro-plating
- improves appearance( gives a shiny, attractive finish)
- corrosion resistance
- increase durability
- reduces friction
- enhances conductivity
- cost efficiency
Disadvantages of electro-plating
- environmental impact (involves hazardous chemicals)
- high setup cost
- risk of uneven coating
- not suitable for all materials
- very time consuming process
Uses of electro-plating
- machine parts
- tools
- watches
- connectors and circuit boards
- mobile phone parts
- car parts (bumpers)
- kitchenware and bathroom fixtures
- coins.
Advantages of powdered coating
- durability (produces thick and tough coating)
- environmentally friendly
- coating applied evenly
- variety of finishes
- cost effective over time
- faster processing
