Protective coatings on magnesium and its alloys — a critical review

The main objective of this review is to describe some of the important topics related to the use of marine and protective coatings for anticorrosive purposes. In this context, “protective” refers to coatings for containers, offshore constructions, wind turbines, storage tanks, bridges, rail cars, and petrochemical plants while “marine” refers to coatings for ballast tanks, cargo holds and cargo tanks, decks, and engine rooms on ships. The review aims at providing a thorough picture of state-of-the-art in anticorrosive coatings systems. International and national legislation aiming at reducing the emission of volatile organic compounds (VOCs) have caused significant changes in the anticorrosive coating industry. The requirement for new VOC-compliant coating technologies means that coating manufacturers can no longer rely on the extensive track record of their time-served products to convince consumers of their suitability for use. An important aspect in the development of new VOC-compliant, high-performance anticorrosive coating systems is a thorough knowledge of the components in anticorrosive coatings, their interactions, their advantages and limitations, as well as a detailed knowledge on the failure modes of anticorrosive coatings. This review, which mainly deals with European experience and practice, includes a description of the different environments an anticorrosive coating system may encounter during service. In addition, examples of test methods and standards for determination of the performance and durability of anticorrosive coatings have been included. The different types of anticorrosive coatings are presented, and the most widely applied generic types of binders and pigments in anticorrosive coatings are listed and described. Furthermore, the protective mechanisms of barrier, sacrificial, and inhibitive coatings are outlined. In the past decades, several alternatives to organic solvent-borne coatings have reached the commercial market. This review also presents some of these technologies and discusses some of their advantages and limitations. Finally, some of the mechanisms leading to degradation and failure of organic coating systems are described, and the reported types of adhesion loss are discussed.

Anticorrosive coatings: a review

The homogeneous combination of inorganic and organic moieties in a single-phase material provides unique possibilities to tailor the mechanical, electrical, and optical properties with respect to numerous applications. The synthetic pathway follows the well-known sol−gel procedure. Nevertheless, the establishment of defined hybrid products necessitates a basic understanding of the underlying chemistry as well as of the parameters influencing the processing techniques. Modern spectroscopy provides versatile tools, e.g., multinuclear NMR experiments and Raman scattering to investigate the sol−gel processing of organo(alkoxy)silanes in their co-condensation reactions with main group or transition metal alkoxides as well as in their copolymerization reactions with each other or with organic molecules. This almost infinite modular design concept has led to the industrial application of coatings for transparent plastics, glasses, and metals to prevent these substrates from mechanical abrasion, permeation, or co...

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Hybrid Sol−Gel-Derived Polymers: Applications of Multifunctional Materials

The present invention is directed to compositions (“Nanomaterial Polymer Compositions”) comprising a silicone polymer and a nanomaterial, including but not limited to, a single or multi-walled nanotube, a nanowire, a nanodot, a quantum dot, a nanorod, a nanocrystal, a nanotetrapod, a nanotripod, a nanobipod, a nanoparticle, a nanosaw, a nanospring, a nanoribbon, a branched nanomaterial, or any combination thereof. The Nanomaterial Polymer Compositions are useful for optical and sensing devices including but not limited to noise suppression, passive Q-switching, mode-locking, waveform shaping, optical switching, optical signal regeneration, phase conjugation or filter devices, dispersion compensation, wavelength conversion, a soliton stabilization, microcavity applications, interferometers; optical, magneto-optical or electro-optical modulation; and biochemical sensors and photodetectors. The Nanomaterial Polymer Compositions are also useful in soft lithography processes.

Nanomaterial polymer compositions and uses thereof

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

Nanoparticles containing hybrid materials became of interest for many areas in the last decade. The reason for this is the fact that, in addition to the molecular inorganic-organic hybrid network, the physical, electronical, optical or catalytical properties of nanoparticles resulting from the inorganic crystalline, glassy or metallic properties also can be used for the material tailoring. For this reason, a survey is given over some interesting developments. Furthermore, in case studies, examples are given for the effect of nanoparticles on the two component Ormosil type of hybrids composed of ethyl ortho-silicate (TEOS) and methylethoxy(methoxy)triethoxy silane (MTEOS, MTMOS). It was shown that the 6 nm SiO2-containing nanocomposite hybrid sols can be dried in form of thick films up to 14 μm after a one step dip-coating process and densified crack-free. This is attributed to the increase of relaxation ability and flexibility. This nanocomposite based on TEOS, MTEOS and particulate SiO2 has been used to develop an industrial process for a new type of environmentally friendly glass fiber mat with a temperature resistance up to 600°C.

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The Sol-Gel Process as a Basic Technology for Nanoparticle-Dispersed Inorganic-Organic Composites

A composite adhesive for optical and opto-electronic applications contains the following: (a) transparent polymers and/or polymerisable oligomers and/or monomers suitable for use as adhesive; (b) nanoscale inorganic particles; (c) if required, compounds for the surface modification of the inorganic particles; and (c) if required, a cross-linking initiator. The composite adhesive can be used for connecting individual components of optical or opto-electronic elements and for constructing such elements.

Composite adhesive for optical and opto-electronic applications

The invention relates to a method for producing a composition for preparing nanostructured forms and layers, consisting of bringing an aqueous and/or alcoholic sol of a compound of an element selected from silicon and the main and sub-group metals into contact with species which have hydrolyzable alkoxy groups and which include at least one organically modified alkoxysilane or a precondensate derived therefrom, in conditions which lead to the (further) hydrolysis of the species and then removing any alcohol which has formed or which may optionally have been present originally. The invention is characterized in that enough alcohol is removed to leave a residual amount of not more than 20 wt.% in the composition.

Nanostructured forms and layers and method for producing them using stable water-soluble precursors

To produce functional vitreous, preferably colored or colloid-dyed layers, a composition produced by hydrolysis and polycondensation of (A) at least one hydrolyzable silane of general formule (I): SiX4, where the X radicals are the same or different and represent hydrolyzable groups or hydroxyl groups, or an oligomer derived therefrom, and (B) at least one organosilane of general formula (II): R1aR2bSiX(4-a-b), wherein R1 is a non-hydrolyzable radical, R2 is a radical carrying a functional group, X is as above and a and b have the values, 0, 1, 2 or 3, the sum of a + b having the value 1, 2 or 3 or an oligomer derived therefrom, with an (A):(B) substance ratio of 5-50:50-95, and optionally (C) one or more compounds of glass-forming elements, is mixed with at least one function carrier from the group of temperature-stable dyes or pigments, metallic or nonmetallic oxides, coloring metallic ions, metallic or metallic-compound colloids and metallic ions that react under reduction conditions to form metallic colloids; the composition mixed with the function carrier is applied to a substrate, and the coating is thermally condensed to form a vitreous layer.

Process for producing functional vitreous layers

The preparation of crackfree and transparent Si02 coatings on soda lime glass with thicknesses of about 8 jm after densification at 500 °C is presented. The high thickness can be obtained by using an 80:20 mixture of methyltriethoxysilane and tetraethyl orthosilicate as alkoxide precursors in combination with an aqueous colloidal Si02 sol with particle sizes of about 7 nm. This principle of synthesis is also applied to Zr02 containing coatings yielding to thicknesses of about 3 j.m. Refractive index measurements indicate that the coatings are nearly completely densified. At higher temperatures tensilestresses appear within the layers and are transmitted to the substrate, increasing its thermal stability. 1 . INTRODUCTION Since the possibility of depositing oxide coatings via the sol-gel process was discovered in 19391 , one main aim was to increase the thickness of these layers. This problem involves the synthesis of thecoating solution, the homogeneous deposition of the liquid film, the drying process and the final

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Gerhard Jonschker

Papers

The Sol-Gel Process as a Basic Technology for Nanoparticle-Dispersed Inorganic-Organic Composites

Composite adhesive for optical and opto-electronic applications

Nanostructured forms and layers and method for producing them using stable water-soluble precursors

Process for producing functional vitreous layers

Sol-gel-derived thick coatings and their thermomechanical and optical properties