Surface Preparation, Protection and Maintenance

This section covers the interaction between the chosen materials of the substrate and their geometry, on the one hand, and optimum local surface conditions on the other. These surface conditions are developed to benefit both functional fulfillment and corrosion control, and close co-operation between design engineers, corrosion specialists, and technical experts in individual fields of surface-treatment technology is highly recommended. 

Simple compact, smooth surfaces, optimally shaped, positioned, and angled are preferred to haphazardly complex and rough-textured configurations of planes, which are prone to accumulation and retention of dust, debris, and moisture, cause difficulties in rendering the requisite anti-corrosion precautions, which are affected by adverse phenomena such as impingement, turbulence, gas-bubble formation, and the creation of concentration cells. Rounded contours and corners provide the best continuity of surface and are preferred to surfaces forming sharp angles. 

HydrodynamicaUy shaped surfaces are favored in flowing seawater and other corrosive liquids, and aerodynamicaUy shaped surfaces in the atmosphere and corrosive gaseous environments, especially at high velocities. 

Corrosion and Materials Selection A Guide for the Chemical and Petroleum Industries, First Edition. Alireza Bahadori. 2014 John Wiley Sons, Ltd. PubUshed 2014 by John Wiley Sons, Ltd. 

The continuity of profile flow can be further secured with the help of the following design precautions  

---

Originally specified with a 10-15 year performance, the oldest systems on the Midland Links are over 15 years old and will be in need of major maintenance within a 20 year life. Some areas have performed badly due to excessive water exposure. Some poor quality products have been used and in some cases inadequate surface preparation has given problems. On the M4 elevated section cathodic protection trial a water-based and a solvent-based coating were applied back to back . This trial should be evaluated after five years of operation. 

Expressions such as cost/or cost/m /y, which is better, percent of maintenance costs, percent of capital costs, and so forth, are often used to describe the cost of coating systems in economical terms. However, all these expressions provide an incomplete comparison on which to base a business decision. The cost of coatings materials for a maintenance overhaul only range between 5 to 21 percent of the total costs, while surface preparation is constant at about 45 percent of the total. Additionally, the performance of protective coatings has to be included in the overall decision matrix. High-performance epoxy polyamide, urethane, or zinc-rich systems, for example, may represent savings of nearly 40 percent over "less expensive" systems when a service life greater than 10 years is considered. 

---