Corrosion

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Presentation Transcript

CORROSION : 

CORROSION

CORROSION : 

CORROSION Corrosion is a chemical change, in which a metal loses its properties because of a chemical reaction with its environment. Corrosion is a very slow process, can take decades depending on the metal involved. Corrosion looks different for different types of metals.

IRON (Rusting) : 

IRON (Rusting) The corrosion of iron-based metals is called RUSTING Iron reacts with oxygen to form IRON OXIDE The oxygen can come from AIR or WATER

IRON (Rusting) : 

IRON (Rusting) Rusting iron is POROUS

What’s Porous? : 

What’s Porous?

What’s Porous? : 

What’s Porous?

IRON (RUSTING) : 

IRON (RUSTING) So What? Rusted metal will absorb water and “flake off” This exposes fresh un-rusted metal to water or oxygen This new metal will rust Costs billions of dollars

Rust is Porous : 

Rust is Porous

ALUMINUM : 

ALUMINUM Reacts with oxygen in the air to make ALUMINUM OXIDE The aluminum develops a layer of rust, preventing further corrosion.

SILVER : 

SILVER

SILVER : 

SILVER Silver does not rust, but tarnishes very slowly. Silver reacts with hydrogen sulfide found in food or water In this reaction, silver turns into silver sulfide. Silver Sulfide: Called “tarnish” A blue/black colour

Slide 14: 

Spoon made of silver SILVER SPOON COVERED IN SILVER SULFIDE (TARNISH)

SILVER : 

SILVER Let’s make silver tarnish quickly! Materials 1 piece of silver material 2 hard boiled eggs (only the yolk) 1 zip lock bag Procedure Boil eggs, remove egg yolks Place in ziplock bag, overnight in freezer

SILVER : 

SILVER

Preventing Corrosion : 

Preventing Corrosion Key – keep metal surface from having contact with oxygen

Preventing Corrosion : 

Preventing Corrosion Materials to paint: Paint Oil Rust proof paint Prevention is based on stopping the metal from being exposed to OXYGEN in either air or water.