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A New Protocol for Evaluating the Effectiveness of Coatings Used to Reduce Corrosion of Steel Structures

Details of a new protocol for evaluating the effectiveness of coatings to reduce corrosion of steel structures is presented in this paper. Basic concepts of accelerated testing specified in American Society for Testing Materials (ASTM) standards and recent research investigations were used to develop a procedure that can provide conclusive results within 2400 hours of exposure as compared to more than 5000 hours in current practices. 

Product Number: 51220-295-SG
Author: Giri Venkiteela, Perumalsamy Balaguru
Publication Date: 2020
Industry: Coatings
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Details of a new protocol for evaluating the effectiveness of coatings to reduce corrosion of steel structures is presented in this paper. Basic concepts of accelerated testing specified in American Society for Testing Materials (ASTM) standards and recent research investigations were used to develop a procedure that can provide conclusive results within 2400 hours of exposure as compared to more than 5000 hours in current practices. Growth of corrosion from a location where the coating is damaged, thinning of coating, color changes and influence of weld and bolt holes were the parameters used for evaluating the performance of the coatings. The major differences between the proposed method and the current practice are: a circular shaped scribe for creating artificial damage instead of X shape, use of adhesion strength of the coating to obtain corrosion-creep growth at various stages of corrosion and addition of deep-freezing cycle as part of accelerated corrosion to enhance creep growth. The adhesion strengths are much easier to measure as compared to measuring few millimetres of creep growth that are typically fuzzy. The proposed test method was evaluated by comparing the performance of 6 coating systems. These 6 systems were chosen using the results of a 20 -year field study, in which, 2 coatings provided very good corrosion protection while 2 others were found to be very weak. The results show that the proposed protocol provides clear difference between strong and weak coatings and simulates the field behavior well.

Details of a new protocol for evaluating the effectiveness of coatings to reduce corrosion of steel structures is presented in this paper. Basic concepts of accelerated testing specified in American Society for Testing Materials (ASTM) standards and recent research investigations were used to develop a procedure that can provide conclusive results within 2400 hours of exposure as compared to more than 5000 hours in current practices. Growth of corrosion from a location where the coating is damaged, thinning of coating, color changes and influence of weld and bolt holes were the parameters used for evaluating the performance of the coatings. The major differences between the proposed method and the current practice are: a circular shaped scribe for creating artificial damage instead of X shape, use of adhesion strength of the coating to obtain corrosion-creep growth at various stages of corrosion and addition of deep-freezing cycle as part of accelerated corrosion to enhance creep growth. The adhesion strengths are much easier to measure as compared to measuring few millimetres of creep growth that are typically fuzzy. The proposed test method was evaluated by comparing the performance of 6 coating systems. These 6 systems were chosen using the results of a 20 -year field study, in which, 2 coatings provided very good corrosion protection while 2 others were found to be very weak. The results show that the proposed protocol provides clear difference between strong and weak coatings and simulates the field behavior well.

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