<div>Pack rust or crevice corrosion is a type of localized corrosion. When a metal is in contact with a metal, or even non-metal, the metal starts to corrode, and rust starts to pack in between the surfaces. When signicant development of pack rust occurs, it can cause overstressing of bolts and rivets causing them to fail, and it can bend connecting plates and member elements thus reducing their buckling capacity. Thus it is important to mitigate the formation and growth of pack rust in bridges. This study was conducted to determine if pack rust occurs frequently and thereby may pose a problem in the state of Indiana. The study is divided into three primary tasks.The rst part of the study involves understanding the parameters involved in the initiation process of crevice corrosion and post-initiation crevice corrosion process. The second part of the study involves reviewing existing mitigation strategies and repair procedures used by state DOTs. The third part of the study involves identifying steel bridges with pack rust in Indiana. Analyses were performed on the data collected from Indiana bridges that have pack rust. This involved nding the components and members of bridges which are most aected by pack rust and nding parameters which in uence the formation of pack rust. Pack rust in the steel bridges were identied using the INDOT inspection reports available through BIAS system. The study revealed that good maintenance practices helped in reducing pack rust formation. The study identied locations on steel bridges which have a high probability towards pack rust formation. A mitigating strategy possessing qualities which can show promising results is identied.</div>

<p>Pack-rust corrosion is a type of corrosion that affects steel built-up members especially old  bridges. It is a localized corrosion that happens in the crevice between two mating surfaces. Pack-rust corrosion does not only cause section loss like other types of corrosions, but also induces local distortion in the structural members that are not the intention of the original designs. This corrosion can change the behavior of the connection fixity and could also cause instability in the overall  built-up members. The size of distortion and section loss were observed to behave linearly between  the free edge and the first line of fasteners. As the distance is moving toward the free edge, the  distortion in the members and section loss in the base material were observed to be maximum. Another important observation was that pack-rust corrosion does not grow beyond the fastener at the fastener’s line. </p> <p>The literature revealed that there are no comprehensive experimental and analytical studies focused on the behavior and effect of pack-rust corrosion on the overall performance of built-up members and connections in compression. Therefore, this research studies the effects of pack-rust corrosion on the capacity of built-up compression members including but not limited to stiffness, yield strength, maximum capacity, and change in fastener force under applied load. This research was studied by performing large-scale experimental testing of flexural members with simulated pack rust. Pack-rust distortion was simulated by placing washers in the crevice between two plates and then the two plates were drawn together using high-strength fasteners. There were also members with real pack-rust corrosion damage from bridge components that used to be in service, and were tested in axial compression tests. </p> <p>The experimental results were compared with hand calculation using conventional design  equations. Finite element analysis was also studied to compare with the experimental results in  order to calibrate future models, but it is not presented in this report. The findings of the  experimental results of all the specimens show that pack-rust corrosion affects yield strength and  maximum capacity of the member and minimally affects the member’s stiffness. Maximum load  of the member affected by pack-rust corrosion can still be estimated conservatively using the  conventional design equations with some modifications. There was no indication of significant  increase in fastener force under applied load, so the likelihood of fastener failing in tension was  very small as observed from this study.   </p>

<p>As of 2013, the damage caused by corrosion on highway bridges has been estimated to cost approximately 14 billion dollars annually, and this cost has been increasing over the years. Corrosion is one of the natural phenomena that has been slowly deteriorating infrastructure systems across the United States. One of the most problematic types of corrosion is crevice corrosion, which is defined as the formation of rust between overlapping surfaces such as the case of a splice connection where flanges are attached by splice plates. A significant number of steel bridges in Indiana have developed crevice corrosion in splice connections. Therefore, this research focuses on the crevice corrosion, or “pack rust”, occurring in these structural elements. The application of coatings alone has not been enough to stop pack rust at these connections. In an attempt to look for approaches that can effectively mitigate this problem and maintain the designed service life of bridges, different strategies have been studied and tested. The first objective of this study is to determine the strength reduction as a function of the time of exposure to salt misting. To do this, specimens that simulate the bottom flange splice connection have been exposed to a corrosive environment for different periods of time and later tested under tension to assess the reduction in strength. The second objective is to evaluate the effectiveness of the mitigation strategies under different conditions. First, the mitigating products were initially applied before exposure to salt misting. Second, the mitigating products were applied as a repair, and in this case, the specimens corroded for a given period of time and were then repaired to evaluate any further deterioration. The assessment of the strategies’ effectiveness is based on the strength reduction and visual inspection of the specimens. The ultimate outcome of this study is a series of general guidelines to slow down crevice corrosion based on the results of the laboratory testing. </p>