Metalic corrosion causes many problems. Aluminium has a very high resistance to corrosion, because it is covered spontaneously by a thin but effective coating of oxide which protects it from further oxidation. The Aluminium oxide is impermeable and is integral with the base metal. If the coating of oxide is damaged mechanically this coating will be renewed immediately. The coating of oxide is a main reason for the good corrosion characteristics of Aluminium. The coating stays stable for pH-values between 4 - 9.

Aluminium corrodes easily, especially when exposed to moist or acidic environments. The most frequent types of corrosion are Galvanic Corrosion, Pitting and Crevice Corrosion. Typical ways of preventing it from corrosion involve creating a protective barrier by coating its surface. Chromate is particularly effective for this purpose but the hexavalent chromium has carcinogenic properties and more inert coatings are sought.

The self-assembled monolayer of an environmentally friendly hydrophobic organic material can provide initial protection but it has limited thermal stability and has molecule-sized defects.

As an alternative to conventional materials, laurate- intercalated films of ZnAl layered double hydroxide (ZnAl-LDH-laurate) were fabricated by anion exchange of laurate with ZnAl-LDH-NO3- films on a porous anodic alumina/aluminum (PAO/Al) substrate. The presence of both microscale and nanoscale hierarchical structures (SEM Fig- 4) makes the film superhydrophobic, and thus it has much better corrosion resistance than anodic PAO film alone or ZnAl-LDH-NO3- films. That is, LDHs are very versatile materials and the ability to vary their composition over a wide range allows materials with a range of properties to be prepared. (F. Zhang, L. Zhao, H. Chen, S. Xu, David G. Evans, X. Duan; Corrosion resistance of superhydrophobic layered double hydroxide films on aluminum. Angew. Chem. Int. Ed. 47, 2466–2469; 2008)

Firstly, for forming a film of ZnAl-LDH-NO3–, porous anodic alumina have to fabricated by anodizing an aluminium substrate and placing it in an alkaline solution of zinc nitrate (NO3–) with excess nitrate ions. The substrate was the source of the Al3+, for this a tightly bound film with good mechanical stability was formed. Immersion in an aqueous solution of sodium laurate resulted in a tilted bilayer of laurate anions between layers of the LDH.

Scanning electron imaging showed the surface to be rough due to both nanoscale LDH hexagonal platelets oriented perpendicular to the surface (Fig- 2), and macroscale protrusions with a similar surface morphology (Fig- 3); the protrusions were assumed to result from thickening of the LDH crystallites due to the incorporation of the laurate anions. Water droplets on this rough surface sit on a combination of the platelets/protrusions and air, with a contact angle of 163°, which is  within the realm of superhydrophobicity.