Sol–gel derived films exhibit a high potential as substitutes for the environmentally unfriendly chromate metal-surface pre-treatment methods. Inorganic sol–gel derived films offer good adhesion between metals and organic paint. However, they cannot provide adequate corrosion protection due to their high crack-forming potential. Introduction of an organic component to an inorganic sol–gel system leads to the formation of thicker, more flexible and functionalized films with enhanced compatibility to different organic top coatings. Incorporation of nanoparticles in the hybrid sol–gel systems increases the corrosion protection properties due to lower porosity and lower cracking potential along with enhancement of the mechanical properties. Furthermore, the incorporation of inorganic nanoparticles can be a way to insert corrosion inhibitors, preparing inhibitor nanoreservoirs for “self-repairing” pre-treatments with controlled release properties.

Sol–gel coatings for corrosion protection of metals

Inorganic–organic hybrid coatings by sol–gel process are very suitable for fighting corrosion. Inorganic sols in hybrid coatings not only increase adhesion by forming chemical bonds between metals and hybrid coatings, but also improve comprehensive performances of polymer in the coatings. Different organic polymers or organic functionalities are introduced into gel network to achieve tailored properties, such as hydrophobic properties, increasing cross-linking density, etc. As for corrosion protection of metals organic components of hybrid coatings are selected to repel water and form dense thick films and reduce coating porosity. The factors, such as the ratio of inorganic and organic components, cure temperature, pigments in hybrid coatings, need to be optimized for attaining hybrid films with the maximum corrosion resistance. Electro-deposition technique offers relatively thick homogeneous defect-free hybrid coatings in comparison to dip or spin coating techniques. Green cerium ions and non-ionizable organic inhibitors are more developed in hybrid coatings nowadays than other corrosion inhibitors. Long-term corrosion resistance techniques of inhibitors are discussed. The inhibitors entrapped in the nanocontainers are doped in hybrid films to prolong release of the inhibitors to damaged zones, which is discussed in detail. Among all the nanocontainers of corrosion inhibitors the prospective techniques which show superior corrosion protection are cyclodextrin/organic inhibitor inclusion complexes and layer by layer assembly of organic corrosion inhibitors in nanocontainers. Super-hydrophobic property of hybrid coatings derives from low surface tension and surface roughness of hybrid coatings, which endues the films with excellent corrosion protection for metals, but the durable property of super-hydrophobic coatings needs to be improved for industrial application. An ideal multiple model of hybrid coatings for superior anti-corrosion of metals proposed is a combination of super-hydrophobic hybrid coatings and underlying hybrid coatings doped with sustained release of corrosion inhibitors on metal substrates.

Inorganic–organic sol gel hybrid coatings for corrosion protection of metals

Electrodeposition of sol–gel films on Al for corrosion protection

Nanotopographical Surfaces for Stem Cell Fate Control: Engineering Mechanobiology from the Bottom.

Electromagnetic interference shielding effectiveness of electroless Cu-plated PET fabrics

Formation of Al–Zr composite oxide films on aluminum by sol–gel coating and anodizing ☆

Local deposition of copper on aluminum was attempted by the successive processes of anodizing, laser irradiation, and electroless plating. Aluminum specimens covered with anodic oxide films were immersed in Cu 2+ , Cu 2+ /H 2 PO 2 - , and diluted NaOH solutions, and irradiated with a pulsed yttrium aluminum garnet (YAG) laser. The time variation in the rest potential of the specimens was followed during laser irradiation by a potentiometer, and the change of the surface composition by laser irradiation was examined by X-ray photoelectron spectroscopy (XPS). After the laser irradiation, copper electroless plating was carried out in (Cu 2+ , Ni 2+ )/H 2 PO 2 - solutions with or without Pb 2+ or thiourea. The rest potential measurements and XPS analysis suggested that Cu particles nucleate at the film-removed area by laser irradiation in Cu 2+ and Cu 2+ /H 2 PO 2 - solutions. A copper layer was obtained at the irradiated area by the subsequent electroless plating, and the copper nuclei acted as catalytic centers at the very initial stage in copper electroless plating. The effects of Pb 2+ and thiourea concentration and the deposition temperature on the kinetics of copper deposition is also discussed.

Copper Electroless Plating at Selected Areas on Aluminum with Pulsed Nd‐YAG Laser

Electroless plating of Ni‐P has been widely applied, since it is not selective to substrate materials with respect to electric conductivity and can provide excellent coverage of the substrate, especially those with complicated shapes. Much effort has been made to understand the deposition process, the effects of additives, and the structure and properties of the deposits in Ni‐P electroless deposition. 1‐9 In electroless plating, activation of the substrate is an indispensable pretreatment to initiate the reduction of nickel ions and to improve adhesion between deposit and substrate. Successive immersion in SnCl2 and PdCl2 solutions is a conventional activating process before the Ni‐P electroless plating. Here the specimen is initially immersed in SnCl 2 solution for 1‐2 min at room temperature to adsorb Sn 21 ions on the surface. During the second immersion in PdCl2 solution, Pd 21 ions are reduced by Sn 21

Local Deposition of Ni‐P Alloy on Aluminum by Laser Irradiation and Electroless Plating

Local surface modification of aluminum by laser irradiation

Aluminum specimens covered with anodic oxide films were scratched with an atomic force microscope (AFM) probe in air, pure water, CuSO 4 solutions, Cu-electroless plating solution, and diluted NaOH solutions to examine the effect of the probe load, scratch number, and processing environment on the rate of groove development. The rest potential of the aluminum was monitored during scratching in the solutions, and in situ AFM observations were carried out after the scratching. Probe wear was alsc examined in pure water and NaOH solution. The rate of groove development was in the order NaOH > CuSO 4 > air = purewater > Cu-electroless solution, and decreased with decreasing probe load and increasing scratch number. The rest potential remained steady in the solutions during scratching with loads below 12.5 μN, while it dropped rapidly above 25 μN. Copper Was deposited in and around grooves during scratching in Cu-SO 4 and Cu-electroless plating solution at the high loads, and after the scratching copper deposits grew only during immersion in Cu-electroless plating solution. Probe-tip wear was greater in NaOH solution than in distilled water.

H. Takahashi

Papers

Formation of Al–Zr composite oxide films on aluminum by sol–gel coating and anodizing ☆

Copper Electroless Plating at Selected Areas on Aluminum with Pulsed Nd‐YAG Laser

Local Deposition of Ni‐P Alloy on Aluminum by Laser Irradiation and Electroless Plating

Local surface modification of aluminum by laser irradiation

Fabrication of Grooves on Aluminum Surface with Atomic Force Microscope Probe Processing