Corrosion barriers coatings

Coatings based on vinyl-epoxies are used as corrosion barrier coatings for storage tanks containing corrosive chemicals. Vinyl-epoxies are a very efficient and long-lasting means of protection for the repair of cured-in-place pipes. This is comparable to replacing a pipe. 

The need to identify replacements for chromate-based technologies has also resulted in the development of alternatives to resin-based corrosion-inhibiting primers. These are primarily inorganic barrier coating techniques, such as sol-gel processes, which may or may not include corrosion inhibitors. These are discussed in a later section. 

In order to avoid diffusion in the plgment/binder interface, in-terfaclal bonds between lx>th phases should be as water-resistant as possible. If permeability is taken as a measure, properly formulated barrier coatings may coiipare in corrosion protective efficiency with normal coatings, the thickness of vhlch is tvo or three times as high. 

Parylenes can be used for contamination control, that is, securing small particles to prevent them from damaging a surface in a sealed unit barrier coating coaling for corrosion control and as dry lubricants. 

A paint consists of (i) vehicle (ii) pigment and (iii) additives or fillers. A vehicle renders the fluidity to the paint and upon drying leaves a film. A pigment suspended in the vehicle offers the corrosion protection. Additives or fillers enable the dry coating to withstand the environment. Corrosion control by barrier coatings may be envisaged as shown in Figure 1.64. 

Initial attempts to use aluminum for automotive trim were unsuccessful due to the corrosion behavior of the metal. It is therefore anodized for automotive trim applications to provide a protective oxide surface which acts as a barrier coating for corrosion pro tec tion. > 2 Aluminum and its alloys are susceptible to pitting and crevice corrosion in chloride containing environments. The corrosion resistance of anodized aluminum is therefore highly dependent on the quality of the anodized surface and the absence of scratches and other damage sites. 

Corrosion causes many plant problems. An understanding of electro-chemical principles is necessary in order to choose the best mitigation measures such as barrier coatings, inhibitors, and cathodic protection. Reference [11] provides further information. 

Hare, C. H. "Anti-corrosive Barrier and Inhibitive Primers" Unit 27, Federation Series on Coatings Technology, Federation of Societies for Coatings Technology Philadelphia, 1978. 

Zirconium dioxide, Zr02, displays a variety of desirable properties including hardness, chemical durability and corrosion resistance. It is employed in numerous applications such as coatings for cutting tools, optical filters, thermal barrier coating, interfacial coatings in fiber reinforced ceramic matrix composites, dielectric films in microelectronics [24] and other applications such as mirrors [25] and sensors [26]. 

---