Preventing corrosion and ice accretion on aluminium surfaces applying organic and inorganic thin films /

Abstract

Ice and wet-snow accretion on outdoor structures, including power transmission and distribution equipment, is a serious problem for regions experiencing icing conditions.Various de-icing and anti-icing techniques have been developed to date to counter this problem. Most of the techniques currently in use, however, including active de-icing methods, are employed only where accumulations are substantial. Passive approaches to the problem such as anti-icing or icephobic coatings which inhibit or retard ice accumulation on the surfaces are gaining in popularity.Metal corrosion should also be taken into account since metal or metallic alloys are subject to corrosion problems when placed in a humid or aggressive environment; the development of any ice-releasing coatings on Al structures, as they must be durable enough, is thus closely related to anti-corrosive protection of that specific metal.Consequently, this research has made an attempt to prepare coatings, either one layer or multi-layer, for use on polished AA6061 and AA2024 substrates combining the qualities of reduced ice adhesion and improved corrosion resistance. These two alloys are among the most widely used aluminium alloys in transportation systems (including aircraft), electric power industry, military, etc. Both the stability of the coatings in a humid environment and their overall ice-repellent performance was systematically studied.This research work has made a systematic approach to investigating the influence of surface roughness on the ice-releasing potential and the hydrophobic properties of the prepared coating surfaces. All coatings displayed a gradual loss of their hydrophobic properties after ~ 1000 h of immersion in water, and while corrosion of surfaces was also observed, except in the case of surfaces treated with permanganate conversion coatings which provided satisfactory anti-corrosive protection. IllAll flat coated surfaces demonstrated shear stress of ice detachment values which were at least ~ 1.5 times lower than uncoated mirror-polished Al surfaces and about ~ 2 times lower than those observed on as-received Al surfaces. The adhesion reduction factor (ARF) values decreased after as many as 12 icing/de-icing events, implying a certain amount of decay of the coatings.All rough superhydrophobic samples allowed for ice adhesion shear stress values of at least ~ 4 to 7 times lower than those obtained on the uncoated as-received Al surfaces. After 24 icing/de-icing experiments, however, ice adhesion strength increased significantly on those surfaces by a factor of ~ 2 after 24 icing/de-icing cycles.In addition, all flat and rough-coated surfaces gradually lost their hydrophobic properties after nearly each icing/de-icing cycle. Thus, the ice-releasing ability of all samples tested was found to be time-dependent.The work thus reveals that it is possible to prepare coatings which provide the reduced adhesion of ice to Al surfaces, while at the same time also providing some degree of anticorrosive protection.

Contribution à l'étude des mécanismes de l'adhésion de la glace à différents matériaux et application à l'évaluation des matériaux glaciophobes /

“…Des études ont été menées pour tenter de comprendre le rôle de la rugosité d'une surface solide sur l'adhésion de la glace en utilisant le concept de la superhydrophobicité [7,17,20], En présence de forts degrés de rugosité, une diminution de l'adhésion de la glace a été remarquée. Cette diminution est liée à la présence de bulles d'air à l'interface de la glace et du substrat [28][29][30][31][32][33]. Par ailleurs, la glace peut adhérer fortement à certaines surfaces car l'eau surfondue pénètre dans les zones poreuses et occupe plus de volume en se solidifiant, créant ainsi un effet d'ancrage mécanique au substrat.…”