Coating selection maintenance

Glycol ether evaporation rates, resin solvency, and surface tension effects on the coating are all important considerations when selecting the solvent system for automotive primers, enamel base and top coats, in industrial maintenance coatings, and wood coatings. Selection of the proper solvents for resin solvency can be greatly simplified by utilizing the Hansen solubility parameter theory. 

Protection by separation of surface from environment by protective coating should be evaluated together with relevant parts of compatibility, mechanics, and surface. Further the problems and limitations of the applicator, climatic and working conditions, properties of materials in relation to procedures and schedules should be reviewed application methods to suit the geometry chosen systems that permit maximum application of money-saving practices, use of the minimum number of different materials and least number of colors selected maintenance practice anticipated. 

Many finishes exhibit low maintenance requirements (e.g. plasticzed metallic sheeting, epoxy coatings, continuous tiling systems, etc.). Others may be more maintenance intensive and may provide lower durability. However, selection must also consider the other operating parameters such as acoustic performance (which may mandate heavier mass or more porous-surfaced materials) or load-bearing capabilities, etc. 

It can be concluded that selection of proper material or lining for seawater application is important and depends on the criticality of the system, availability of standby system/equipment and availability of isolation devices for maintenance. For process piping in seawater application the success of proper lining or coating material depends on the suitability for in-situ/field application and the proper corrosion monitoring plan. 

Errors observed in the use of ISEs fall into three categories. First are errors caused by lack of selectivity. For instance, many CE electrodes lack selectivity against other halide ions. Second are errors introduced by repeated protein coating of the ion-sensitive membrane, or by contamination of the membrane or salt bridge by ions that compete or react with the selected ion and thus alter electrode response. These necessitate periodic changes of the membrane as part of routine maintenance. Finally, the electrolyte exclusion effect, which applies only to indirect methods and is caused by the solvent-displacing effect of lipid and protein in the sample, results in falsely decreased values (see the section on the electrolyte exclusion effect later in this chapter). 

Smart sensors are available that have built-in microprocessor-based diagnostics. For example, smart pH sensors are available that can identify the buildup of coatings on the pH electrode surface and trigger a wash cycle to rednce the effect of the coatings. In general, smart sensors are moderately more expensive than conventional sensors, but, when they are properly selected and implemented, they can be an excellent investment in terms of greater sensor reliability and rednced maintenance. Best practice for instrnment selection, for instrument installation, and to reduce maintenance costs has been identified for the CPI. 

Corrosion control can be accomplished in the design and manufacturing phase as well as in the operation and maintenance phase of the aircraft. Proper design for corrosion control must include the selection of materials, coatings, sealants, and corrosion inhibitors. It is also necessary to avoid dissimilar metal contacts, access for maintenance, and proper drainage. 

Successful application of cathodic protection depends upon the selection, design, installation, and maintenance of the system. Before designing the cathodic protection systems, adequate field data must be collected, analyzed, and evaluated. Nature and conditions of the soil are reflected by field measurements like soil resistance, hydrogen ion activity (pH), and the redox potential. To understand the nature of the pipeline, potential measurements, coating resistance, and meaningful design current requirement tests must be conducted. 

It is essential to make an important decision on the selection of the CP system to be instaUed. The choice of the CP system is based on the environment in which the pipeline is operated. The merits of each system are iUustrated in Section 15.2.3. Sacrificial protection is generaUy employed in environments with low soil resistance (10,000 Q cm) with a relatively low protective current requirement because of the low driving voltage. WeU-coated and isolated pipeUnes favor the instaUation of a sacrificial system in high resistive soils. On the other hand, ICS are usuaUy instaUed in conditions where the current requirements are higher and for pipelines that are bare or poorly coated. In aU cases, the final decision is based on the total instaUation and annual maintenance cost of the systems. 

---