Electrochemical performance of polypyrrole coatings electrodeposited on rheocast aluminum-silicon components

• Electropolymerization of polypyrrole coatings in the presence and absence of sodium nitrate was applied on rheo-cast Al-4.5% Si alloy and pure aluminum. The results showed that the eutectic silicon phase and intermetallic particles in the alloy's microstructure increase the electrodeposition rate in comparison to the pure aluminum substrate. The electrochemical and microstructural studies show that the polypyrrole coatings are able to protect the surface due to the barrier properties and the passivation protection provided by the reduction of the conductive polymer. The coating electrodeposited from sodium nitrate-containing electrolyte presented improved protection for longer immersion time. Localized formation of a thick oxide layer as a result of the drastic galvanic coupling at the polypyrrole/aluminum interface leads to blister formation and failure of the coating. It was revealed that the coating could be deposited into the porosities produced by the casting related defects, but in most cases, this affects the corrosion protection leading to imminent failure.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Kemiteknik -- Korrosionsteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Chemical Engineering -- Corrosion Engineering (hsv//eng)

Nyckelord

Al-Si alloy

Casting defect

Corrosion protection

Galvanic coupling

Polypyrrole

Aluminum coatings

Aluminum corrosion

Corrosion resistant coatings

Electrodeposition

Electrodes

Electrolytes

Electropolymerization

Galvanic corrosion

Nitrates

Polypyrroles

Silicon alloys

Sodium nitrate

Barrier properties

Conductive Polymer

Electrochemical performance

Inter-metallic particle

Polypyrrole coatings

Aluminum alloys

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