Computer Aided Corrosion Prevention Robrecht.Belis@elsyca.com
Agenda Introduction Corrosion on BIW Corrosion on exterior decorative parts Galvanic Corrosion Ecological impact
Corrosion? Introduction of the protective coating conference: Corrosion is the most harmful and destructive of all chemical processes. Rust not only impairs the appearance and properties of a material, but it also triggers maintenance costs. Protective coating systems serve as one of the most important methods for protecting metal surfaces from corrosion. (See http://www.european-coatings.com/events/protective-coatings) Understanding the importance of corrosion is good, taking care of it is better! Corrosion problems must be solved upfront This is a very complex task, can simulations support this process?
Introducing Elsyca Company Profile Founded in 1997, spin-off of Von Karman Institute and University Brussels HQ in Leuven (Belgium), US office in Atlanta Core is unique state-of-the-art electrochemical simulation platform Offering & Market Engineering services, software and advanced tooling Surface finishing and corrosion protection markets Industries: aerospace, automotive, electronics, marine, oil&gas,
Agenda Introduction Corrosion on BIW Corrosion on exterior decorative parts Galvanic Corrosion Ecological impact
Cost E-coating High impact on cost in case of failure Warranty claims Corrosion problems have negative impact on reputation and future sales Design changes are required Expensive tooling Just adding one hole costs +100 k E-coat chemicals +25 M /year for a high volume factory Reducing 2% saves 0.5M Euro/year on chemicals only Image: Dürr
Development challenges Vehicle design Minimum layer thickness specifications Depends on vehicle design Outside area: too high values Cavities: increasing complexity due to crash, NVH, Conflicting requirements crash, acoustics, E-coating, Validation only possible using destructive tests Need to open cavity structures to measure Prototypes are hand-made and very expensive Other Vehicle may be produced on multiple lines What is optimal voltage program
E-coating simulation Physico-chemical data gathering Simulated current density distribution Infrastructure configuration Process parameters Vehicle Data Voltage program, line speed, vehicle trajectory, etc. Elsyca ECoatMaster Simulated layer thickness
Full Vehicle Simulation Changes Over Time Current density distribution Layer thickness distribution
Agenda Introduction Corrosion on BIW Corrosion on exterior decorative parts Galvanic Corrosion Ecological impact
Example of Chrome Plating Exterior decoration parts are often plastic + metal layer Typical process includes copper, nickel, chrome layers Designers are not familiar with this plating process Plating problems are often build-in by design Recessed areas Sharp edges Plating shops have no or minimal impact on the design Have to deal with it! Risk to result in too low layer thickness Parts start to corrode!
Example: Fog Lamp Bezel
Agenda Introduction Corrosion on BIW Corrosion on exterior decorative parts Galvanic Corrosion Ecological impact
Classification of Corrosion Uniform corrosion Galvanic corrosion Stray current corrosion Crevice corrosion Pitting corrosion Filiform corrosion Fretting corrosion Stress corrosion cracking Microbial corrosion Hydrogen embrittlement... Due to a potential difference between two different metals that are connected through an electrolyte with current flowing from more active metal (more negative potential) to more noble metal (more positive potential) Both for immersed components (bulk electrolyte) as well as for components subjected to a thin film of electrolyte (e.g. caused by rain) Copyright http://corrosion.ksc.nasa.gov
Galvanic Corrosion Current Working Practice MIL-STD-889B Use look-up tables with OCP values (open-circuit potentials) Calculate surface areas of metals Estimate corrosion risk based on the above and experience not rate Even for components with only two materials this can be non trivial...
Galvanic Corrosion Example Cu Fe 50 cm 2 of both 1mm thin film electrolyte salt spray test High Low
Galvanic Corrosion Example Cu Fe 50 cm2 of both High Low This allows fast and objective comparisons between different products
Galvanic Corrosion Current Working Practice But... what if... total surface of different metals remains the same, but the geometrical configuration changes? there are many more than only two different metals? metal surfaces are coated? the material is exposed to different environments? the surface is partially wetted? Can you still rely on the current working practices?
Corrosion Prediction Work Flow
Agenda Introduction Corrosion on BIW Corrosion on exterior decorative parts Galvanic Corrosion Ecological impact
Ecological Impact New regulations (e.g. REACH) Chrome VI and cadmium should be replaced This takes time Impact on the process Production infrastructure Process parameters Impact on the functionality Is corrosion resistance still the same? Does it look the same (e.g. chrome)? Does it have the same surface characteristics?
Understand (New) Electrolyte Defining operational window of electrolyte Sensitivity analysis Anodic and cathodic reaction behavior, efficiency, and conductivity Required as input to electrochemical simulation Deposit quality as a function of current density and hydrodynamic conditions
Replacement Alloy Coatings Evaluation Assuring uniformity of composition for optimum corrosion protection Accelerating qualification cycle by parallel simulation / test program Reducing implementation risks through simulation
Conclusion Computer simulations are available for a variety of applications Corrosion of BIW Corrosion of decorative parts Galvanic corrosion Push for green products have an impact on your process Trial-and-Error has become too expensive and time-consuming Simulation technology exists: USE IT!