That is a pretty tall order and more importantly, I would say that your approach is not a good idea. What you want to model is quite different from what the crack example is about.
Using a hybrid pair style the way you are doing is not such a straightforward choice since you are looking at water, which is quite polar and thus has a significant polarizing impact on the metal (depending on distance) and that has quite an impact on the details of what you can learn from your simulation. I just wrote a more detailed discussion on hybrid potential models in a different topic. It should be applicable to your case, too: Using already existing potentials with GROMOS or OPLS simultaneously - #2 by akohlmey
In your case, however, the metal-water interaction is extremely important and I have serious doubts that a simple Lennard-Jones function is suitable to represent this with sufficient accuracy.
More importantly, you also need to keep in mind that your experiment will likely have very different length and time scales than what is accessible for modeling with MD simulations. So it is questionable, if you can extract useful knowledge from mimicking your experiment but then run it with much smaller dimensions and at a much shorter time.
So rather than making up a model, you should search the published literature for how people have previously extracted useful information from simulations for comparison to similar experiments and what level of agreement they have reached. Please keep in mind that there is a difference between a simulation (that represents real physics) and an animation (that looks like what you expect it should look like). Sometimes, the difference is small, sometimes less so.