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51312-01511-Realistic approach of corrosion protection of ballast water tanks

Product Number: 51312-01511-SG
ISBN: 01511 2012 CP
Author: Gabriele Ferrari
Publication Date: 2012
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$20.00
$20.00
Corrosion protection of ballast water tanks is very precarious because of the aggressiveness of the environment and the difficult accessibility of the areas. Numerous accidents in the past have led to regulatory by the International Maritime Organization (IMO). Regulations include the coatings their application and the pretreatment of the substrate. Practical circumstances in yards during application are often not ideal; therefore it is of interest to investigate if the limits for the parameters which determine the coating performance as fixed by IMO are necessary and realistic. The objective of this study was to verify these limits in particular concerning the presence of shop primer and presence of (in)soluble salts and dust on the shop primer. To simulate the possible circumstances in ballast water tanks different exposure methods have been used: exposure of coated samples to seawater at room temperature cyclic exposure by immersion drying and temperature change. During exposure (up to four weeks) electrochemical measurements such as open corrosion potential and impedance measurements were performed. Moreover current was measured during anodic and cathodic polarization of samples foreseen with a holiday; this is to assess respectively the corrosion propagation and the susceptibility to cathodic delamination. Different commercial coatings have been tested. Results show that presence of intact shop primer (used one from practice) and insoluble salts are beneficial; limits for soluble salt and dust as determined by the regulations are realistic. Results have been verified by in situ inspections in water ballast tanks (ships older than 5 years) together with in situ impedance measurements. The performed laboratory test approach has a potential for standardization. Key words: IMO coatings surface preparation water ballast tanks salts dust electrochemical measurements.
Corrosion protection of ballast water tanks is very precarious because of the aggressiveness of the environment and the difficult accessibility of the areas. Numerous accidents in the past have led to regulatory by the International Maritime Organization (IMO). Regulations include the coatings their application and the pretreatment of the substrate. Practical circumstances in yards during application are often not ideal; therefore it is of interest to investigate if the limits for the parameters which determine the coating performance as fixed by IMO are necessary and realistic. The objective of this study was to verify these limits in particular concerning the presence of shop primer and presence of (in)soluble salts and dust on the shop primer. To simulate the possible circumstances in ballast water tanks different exposure methods have been used: exposure of coated samples to seawater at room temperature cyclic exposure by immersion drying and temperature change. During exposure (up to four weeks) electrochemical measurements such as open corrosion potential and impedance measurements were performed. Moreover current was measured during anodic and cathodic polarization of samples foreseen with a holiday; this is to assess respectively the corrosion propagation and the susceptibility to cathodic delamination. Different commercial coatings have been tested. Results show that presence of intact shop primer (used one from practice) and insoluble salts are beneficial; limits for soluble salt and dust as determined by the regulations are realistic. Results have been verified by in situ inspections in water ballast tanks (ships older than 5 years) together with in situ impedance measurements. The performed laboratory test approach has a potential for standardization. Key words: IMO coatings surface preparation water ballast tanks salts dust electrochemical measurements.
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