NEW EDITION! This book provides an extensive update on the second edition with general coverage of the wide field of corrosion control. It is designed to help readers being initiated into corrosion work and presents each corrosion process or control procedure in the most basic terms. Since the first edition was published in 1970, there have been major advances and changes in the technologies used to combat corrosion damage. Third Edition. NACE, 2018.
This report assesses (1) the rate of corrosion of bare steel with and without cathodic protection, and (2) the effectiveness of various commercially avail able coating systems in preventing corrosion of steel piles in seawater. Eighteen coatings and four sacrificial anodes were tested on 24 sets (three piles per set) of ASTM A 36 or ASTM 690 steel H-piles exposed for 5 years at Buzzards Bay, Massachusetts. Performance ratings were established for the following coatings: organic, organic over metal-filled, organic over metal filled with cathodic protection, metallic organic over metallic, and organic with cathodic protection. It is concluded that sacrificial anodes of zinc and aluminum effectively reduced the corrosion rate of bare carbon steel (ASTM 36) piles in the immersed zone from 0.076-0.102 mm/yr (3-4 mils/yr) to zero, and the coating performing best was coal tar epoxy over zinc-rich primer.
Chloride induced corrosion is the prime reason for the degradation of embedded rebar in reinforced concrete marine structures. The present study experimentally investigates the effectiveness of traditional two-component epoxy (EPX), and moisture-cure polyurethane coatings (MC) applied on the concrete surface in reducing the rate of chloride ingression compared to the conventional concrete with and without mineral admixtures like fly ash and GGBS. Coatings used in the present study are characterized by XRD, EDAX, FEG-SEM, water uptake, adhesion strength and contact angle tests. Rapid chloride migration tests (RCMT) were conducted on concrete with and without coatings. Resistivity offered against the chloride migration monitored during the RCMT test indicated that concrete with MC shown higher resistivity in the initial period and continued to decrease over the test duration at a faster rate, unlike EPX. The non-steady-state migration coefficients of the concrete cured for 28days and coated with MC and EPX coatings were found to be nearly 22% and 48% of that of concrete with SCM cured for 84days respectively. The study is further extended to monitor the corrosion of rebar embedded in coated concrete subjected to corrosion acceleration until the first crack appeared on an uncoated specimen. Variation in current flow, half-cell potentials recorded during the acceleration test and actual mass loss of embedded rebar estimated by gravimetric analysis are presented in this paper.
Polarization measurements were conducted over a 21-year period on bare and coated steel "H" pilings 6 inch by 6 inch by 30 feet (15.2 cm by 15.2 cm by 9.1 m) installed in seawater. A DC power source was used to shift from the corrosion potential of each pile to -0.85V. The amount of potential shift was recorded as 6V. The current (6I) required to shift the potential was measured, and a nonlinear pseudoresistance (6V/6I), called the Cathodic Protection Index (CPI), was calculated. The CPI was compared with the coating condition of the steel pilings as determined visually using ASTM standards. Results of these tests will be presented and discussed.