1.3 Metal Part 2 Flashcards
What must be done to metals before they are painted?
Their surface must be correctly prepared.
It should be degreased and cleaned using paraffin then it is washed with hot water and detergent.
What should be applied to a metal before painting so that it doesn’t rust from the paint?
A primer such as a zinc chromate primer. A oil based undercoat a topcoat can be applied to further reduce the likelihood of rust.
What needs to be done to a piece that needs refinishing but the metal is already rusted?
Remove the rust with wire wool, emery paper or a wire brush, then treat the surface with a primer made to combat rust then apply the oil-based topcoat.
What is a plastic coating?
The process of applying a thermoplastic coating on a metal object.
What is the purpose of a plastic coating?
To provide long lasting corrosion, impact and chemical resistance whilst giving an aesthetically pleasing finish.
What are the differences of plastic coatings when compared to paints?
It gives a thicker layer, is impermeable to water and corrosive chemicals.
What is involved in the process of plastic coating?
Degrease and clean the metal then heat to 180°C. Dip the piece in a tank with fluidized powder and left in for a few seconds. Then the piece is put back into the oven.
What is the purpose of electroplating?
To provide metals with a more decorative, appealing or protective surface finish.
What is the process for electroplating?
The metal object is suspended in an electrolyte which acts as the conductor. The positive voltage supply is attached to a metal rod or plate made from the material that will be used for the plating.
What is anodising?
Anodising is a finishing or protective process associated with Aluminium and is used to thicken the natural oxide film on the surface. Anodising is electroplating in reverse.
How is anodising done?
The aluminium is submerged in the electrolyte solution(water and acid). Different acids are used based on what results you want and the temperature of the solution is controlled depending on the desired properties.
What is enameling?
Enameling uses powdered glass or minerals which are melted to provide metal with a hard colorful, aesthetically pleasing and protective finish.
What is the process of enameling?
The metal is treated then then brushed with a thin adhesive
which disperses when heat is applied. Powdered glass or minerals are then sieved onto the adhesive and the piece is put into a kiln to melt and dry.
What is a lacquer used for?
Protective barrier against tarnishing and oxidization after polishing.
What are the properties of lacquer?
hard, durable finish & clear
How should you treat the surface of a metal before using lacquer?
Clean it using a paraffin or white spirit to remove grease.
