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Once a coating system has been breached, protection is afforded by the availability of inhibitors at the defect site. The onset of subsequent corrosion, therefore, is a function of inhibitor release rate, the ratio of inhibitor to aggressive ions, and consumption of inhibitor in the vicinity of the defect. The parameters affecting each of these processes must be understood in order to appropriately model the onset of corrosion for either a first principles or an empirical approach. The influence of coating properties and environmental conditions on inhibitor exhaustion is discussed below.
The functional life of paint in DoD is defined by the barrier properties and protective corrosion inhibiting capacity of the coating system. The time until corrosion initiation of an underlying substrate can thus be defined in general terms as 1) the time for an external environment to reach the coating/substrate interface through coating porosity, coating cracking, or mechanical damage and 2) inhibitor exhaustion/depletion. In other words, once a coating system has been breached, protection is afforded by the availability of inhibitors at the defect site. In this work, we seek to understand the parameters that influence inhibitor exhaustion. An aluminum alloy Multi-Electrode Array (MEA) probe is used to measure corrosion currents directly as a function of exposure time. Both inhibitor leach rate and residual coating protectiveness are measured as a function of time and compared for four aerospace primer systems. Leaching of inhibitors is measured using Ion Coupled Plasma (ICP) to quantify the amount of inhibitor in a 50 mL exposure cell at fixed exposure intervals. At these fixed exposure intervals, the partially depleted coating systems are then expose in a 1.2 mL cell and the inhibition kinetics measured using the MEA probe. Inhibitor exhaustion times are then defined as the time where there is no longer enough inhibitor leaching from a coating system to protect the MEA. Integration of inhibitor exhaustion test results into modeling approaches is briefly discussed.
In this paper, a case study is presented for a marine structure for which modelling has been used to predict the protection potentials over the life of the structure.
The aim of any digital transformation of integrity management and in particular corrosion control is the improvement of communication efficiency, planning efficiency and maintenance efficiency. Key issues are predictive maintenance and clarity of the information available so engineers can make informed decisions. Therefore it is not just a question of collecting more information but also the way that information is used and shared with the decision-makers.
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Duplex stainless steels (DSSs) are based on the Fe-Cr-Ni system and are constituted of 30 to 70 % ferrite and austenite. They combine high tensile strength, good toughness, weldability, and excellent corrosion resistance including stress-corrosion cracking and resistance to localized corrosion.1-3 DSSs can be classified according to the Pitting Resistance Equivalent Number (PREN = Cr + 3.3 Mo + 16 N) in lean duplex (PREN= 22-27), standard (PREN = 28-38), super duplex (PREN = 38-45) and hyperduplex (PREN > 45).
The threshold hydrogen content of a material regarding hydrogen embrittlement plays an increasingly important role in corrosion research. This value indicates the hydrogen content to which the material can be used without failure. However, when determining the threshold hydrogen content, different test methods, different analysis methods and different interpretations of the results come together. This paper is intended to provide a guideline for the determination of the critical hydrogen concentration of high strength steel wire samples.