Research Tools

Pourbaix diagrams

Potential against pH for the systems I work with in the laboratory. Every boundary is computed from thermodynamic data rather than traced from a figure, so you can move the concentration and watch the fields move with it. Reference electrode is switchable.

Reading one of these

The diagram tells you which species is thermodynamically stable at a given potential and pH. For electrodeposition that is the first question worth asking: whether the metal can deposit at all under the conditions you have set, and what is competing with it. What the diagram will not tell you is how fast anything happens.

Systems 7 diagrams Temperature 25 degrees C Reference SHE, SCE, Ag/AgCl, Hg/HgO, RHE
Nickel

Nickel systems

Ni and water

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The simplest case, with no complexing agent. Nickel ion is the only dissolved species, and the two hydroxides are the solids. Start here.
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Ni, ammonia and water

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Ammonia added as a complexing agent. The nickel ammine complexes open a dissolution window where the plain system would have passivated.
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Ni, citrate and water

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Citrate instead of ammonia. Boundaries are placed by bisection rather than by an analytical shortcut, so the crossings are exact.
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Ni, ammonia, citrate and water

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Both complexing agents together, which is the bath I actually plate from. Nickel, citrate and ammonia concentrations are all adjustable.
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Ni, Mo, ammonia, citrate and water

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The alloy bath, with molybdenum added to the same ammonia and citrate system. The heteropolymolybdate is included, and the molybdenum redox lines are drawn dashed over the nickel fields so you can see where the two overlap. All four concentrations move, and citrate or ammonia can be taken down to nothing to see what the ligand was holding up.
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Other metals

Silver and cobalt

Ag and water

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The silver water system built from Bard Table 6. Two triple points organise the whole diagram, and the silver oxide band appears from the first of them.
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Co and water

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Cobalt on CODATA consistent data from Chivot and co workers. Slide the cobalt concentration to see the corrosion field close as the hydroxide takes over.
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