The corrosive fluids transportation inside carbon steel pipelines is critical due to internal corrosion. To avoid failures barrier corrosion protection techniques are applied by insulating the inner metal wall of the pipe. However when the tubes are welded together the inner coating is damaged by the heat generated during the welding process. As a result the ends of the tubes are uncoated and consequently subjected to corrosion. There are solutions to this problem but all have some kind of inconvenience either by the cost of implementation or the difficulty of application. This work aims to present the results of the tests of the application of an alternative technique: zinc thermally sprayed as sacrificial anode for internal protection of welded joints.
Corrosion in the field manifests over a large timescale so when considering material choices in the design of aerospace systems and subsystems use is often made of accelerated tests such as ASTM B117 salt spray chamber test to rank the possible materials. Even these ‘accelerated’ tests take more than 1000 hours and despite their widespread use are often criticized as a design trade tool since the test environments are considerably different to the expected field environment running the risk of either hiding true corrosion processes or simply being unrealistically challenging for the materials under test.The corrosion community has expended substantial effort in trying to make the tests ‘more realistic’ but in doing so there is considerable debate about whether the tools employed to accelerate the corrosion (thermal cycling high salt concentrations UV exposure etc) actually introduce other corrosion processes that are not even present in the eventual targeted field of operation for the device under test.Computational techniques hold a great deal of promise as a way to understand the effects of different service environments but if the simulations cannot even discern between say an ASTM B117 test and an atmospheric exposure then the simulation results would be of questionable value.The processes involved in corrosion are many and complex however one key parameter is the electrolyte film thickness which will clearly be different whether inside a chamber at high humidity with a continuous supply of sprayed saltwater compared to exposure on a beach where diurnal cycles result in a very thin electrolyte of varying salt concentrations except of course when it is raining!To help designers quickly assess corrosion risk and choose appropriate materials Corrdesa have already developed an electrochemical database of modern alloys and coatings. This has been extended by deconvoluting the polarization data to accurately account for the impact of the actual electrolyte thickness on the oxygen reduction reaction.In this paper using fluid shell elements in a free surface flow formulation we actually predict the variable electrolyte film thickness in a CFD (Computational Fluid Dynamics) code for a given environmental condition on different test specimens and geometries. The appropriate polarization data for the local electrolyte thickness is then implemented with User Functions in a potential model framework. In this way the galvanic corrosion is simulated for a test device with a more realistic and variable film thickness.The result is that we can dial different test conditions into the simulation such as whether we wish to simulate chamber results or field results cyclic salt fog cyclic humidity (or both).Keywords: Computational Corrosion Analysis Galvanic corrosion prediction FEA corrosion prediction polarization data potential model fluid shell elements CFD
Understanding environmental conditions experienced during shipping (both domestic and export) and/or storage is critical when determining the most effective corrosion control system for metal components. Temperature and humidity sensors were used to help understand the conditions within industrial packaging applications during different overseas shipping routes and during warehouse storage. The effect of secondary packaging (i.e. polyethylene film) on temperature and humidity within a package was also evaluated. The scope of this paper is to compile and analyze the data and utilizing it to help develop the best corrosion prevention strategies.Key words: Sensor corrosion control packaging overseas shipping
The AC interference between High Voltage AC (HVAC) power lines and pipelines has been modelled with various software programs all of which have a variety of input data which results in various results and outputs.Important aspects such as the soil resistivity along the pipeline route can have a significant impact on the pipelines coating resistance. This in turn affects both the computed AC voltages and current densities both of which can significantly affect personal safety and corrosion of the pipeline.Therefore the spacing between these field measurements along the pipeline route can have a significant effect on the pipeline integrity. Soil resistivity measurements collected every 1000ft versus every 5280ft (1 mile) can have a dire consequence on the corrosion results and the matter is exacerbated where these soil resistivity measurement values change significantly along the route. The accuracy of the soil resistivity field data relative to the actual routing (wetlands rivers low and high resistivity’s etc.) will also affect the correct placement of the AC Mitigation (grounding) as well as the resistance of the grounding which in turn has a cost implication to the asset owners and/or operators.Other aspects such as the power line LEF/EMF may also be used to “calibrate” the AC Interference especially where load data is absent.This paper addresses the critical importance of collecting adequate data for the AC Interference studies to prevent costly installations and to mitigate the incorrect positioning of AC Mitigation systems due to inadequate information.
The application of Corrosion Resistant Alloys (CRA) in harsh environments and severe services is gaining a leading position across the Industry. Among the different CRA Duplex & Superduplex stainless steels (DSS) represent an often-interesting choice in terms of cost-benefit ratio. Duplex and superduplex stainless steels as a matter of fact offer a competitive cost excellent corrosion resistance in many environments and good mechanical properties; they are often replacing and upgrading traditional stainless steels by closing the application gap with more noble alloys such as nickel and copper alloys. The quality control of DSS fabrications that involve welded joints cannot underestimate the possible influence of the welding process itself on the localized corrosion resistance of the material. Such alloys are characterized by a somewhat complex metallurgy which involves during welding the possible precipitation of undesirable phases & compounds that can induce an important loss of corrosion resistance in particular considering localized corrosion phenomena (e.g. pitting corrosion).During welding and materials qualification steps the most commonly specified test for checking localized corrosion resistance of CRA in particular in chloride-containing environments is the Ferric chloride ASTM G48  corrosion test. So many End-User material & fabrication specifications have taken up this procedure by incorporating it and often customizing it. This is because the procedure described in the ASTM standard does not cover or define in detail many particular aspects of the test itself. This creates a number of free interpretations of the test procedure that can be associated with more or less severe test conditions and more or less easy-to-reach requirements. It can be useful to remember that the test itself is in any case not a real fitness for purpose test but more a quality control one; it is carried out under very severe conditions often more severe than the actual conditions in which components will be exposed. This also means that even small variations in the test procedure welding variables or welding metallurgy can tip the balance in the pass/fail equilibrium. The purpose of this work is to describe some fundamental aspects of test procedure and results evaluation somehow customizable with respect to the ASTM standard which may influence the test outcome itself also considering a possible review of the standard toward a more unified procedure. In this context taking into account that manufacturers find themselves in need to optimize the welding process with the aim to overcome G48 corrosion test during qualification the work also describes typical issues related to welding that could induce a negative verdict of ferric chloride pitting test.
For many decades corrosion resistant Copper Alloys have been utilized in sea water applications for their unique combination of properties anti-biofouling non-sparking resistance to cavitation corrosion excellent wear properties and low magnetic permeability.One disadvantage has been lack of mechanical strength and Copper Nickel Chromium (CuNi30Cr2) is a unique alloy developed to overcome this. It does not rely on a precipitation hardening mechanism for increasing the mechanical properties but “spinodal” decomposition which is a chemical strengthening mechanism. Additionally the alloy is single phase and hence it does not suffer from selective phase corrosion which has been problematic with some copper based alloys in marine salt water environments.This paper evaluates the wrought version of CuNi30Cr2 which can now be manufactured to Def Stan 02-886 and offers significant scope for design engineers with much higher mechanical properties increased toughness and increased internal integrity. It provides the findings of a four year corrosion program with comparisons against 26 other alloys involving a range of copper alloys Monel® Inconel® Super Duplex Titanium and Stainless Steels. General corrosion galvanic and crevice corrosion in a sea water environment were all examined as well as mechanical properties.