Session Details

Session 11: Corrosion & Wear Deposit Coatings

Abstract Number:

54

Al and AlMn alloys were studied as alternative coatings to cadmium ‎coatings. The AlMn alloy offered better corrosion protection than the Al ‎layers, pristine or passivated, and this result was confirmed by the ‎polarization resistance values and lower corrosion current densities ‎obtained by linear sweep voltammetry and EIS measurements. The alloy ‎containing 40 at% of Mn offered the best corrosion resistance for steel; ‎it was even superior to a passivated Cd layer.‎

Topics:

Corrosion or Wear Deposits/Coatings
General Surface Finishing

Al and AlMn alloys were studied as alternative coatings to cadmium ‎coatings. The electrolyte used in this study consisted in a mixture of ‎AlCl3 and [EMIm]Cl (1-methyl-3-ethyl-imidazolium chloride) in a molar ‎ratio of 2:1, in which 0.2 and 0.4 mol/L MnCl2 were dissolved. All the ‎measurements were performed inside a glove-box filled with Ar.‎

The electrodeposition of Al and of AlMn alloys occurs with a current ‎efficiency close to 100% from the electrolytes chosen. There was a ‎significant difference between the morphology of the Al layers and that ‎of the AlMn alloys. The Al layers consist of microsized grains, while the ‎AlMn alloys are much smoother and more compact. One can also tune ‎the morphology of the deposits by tuning the current density. Thus, at ‎low current densities, below 5 mA/cm², one could obtain rough layers, ‎while smoother ones were deposited at current densities above 6 ‎mA/cm². Al films were crystalline, while the AlMn alloys were often ‎amorphous.‎

Al and AlMn films showed good corrosion protection properties and can ‎be used as alternative coatings to Cd. The AlMn alloy offered better ‎corrosion protection than the Al layers, pristine or passivated, and this ‎result was confirmed by the polarization resistance values and lower ‎corrosion current densities obtained by linear sweep voltammetry and ‎EIS measurements. The alloy containing 40 at% of Mn offered the best ‎corrosion resistance for steel; it was even superior to a passivated Cd ‎layer.‎

This study shows that dense and fine-grained Al and AlMn layers can be ‎plated from ionic liquids. Their corrosion behavior in 3.5% NaCl proved to ‎be comparable to that of cadmium. However, in order to make this ‎process attractive for industry, one should further optimize the plating ‎rate and reduce complexity of plating procedure.‎

ELECTROCHEMICAL DESPOSITION OF ALUMINUM AND ALUMINUM-MANGANESE ALLOYS IN IONIC LIQUIDS

Adriana Ispas, Ph.D.

Technische Universitaet Ilmenau