How do you translate a Pourbaix diagram accurately when the graphic uses electrode potential, pH, labelled chemical species and boundary lines to describe corrosion? The reliable method is to read it as an equilibrium map before replacing a single technical term. A Pourbaix diagram, also called an E–pH or potential–pH diagram, identifies thermodynamically favoured forms of an element in aqueous conditions. Its fields do not directly report a corrosion rate, and its lines cannot be understood correctly without their reference scale and assumptions.
Readers looking for how to read or translate Pourbaix diagrams commonly need help with the potential axis, the meaning of immunity and passivation regions, the difference between aqueous ions and solid oxides, or how to describe a boundary crossing in another language. These are not merely vocabulary problems. A translation can sound fluent while moving the point to a different stability field, changing an oxidation state or suggesting that a passive coating is guaranteed. This guide shows a source-to-target workflow that protects the chemistry.
Start with the original figure and caption. Record the metal system, solution conditions, temperature, potential reference, dissolved-species activity or concentration convention, visible water-stability lines and all phase labels. Only then formulate sentences for a learner, technician, interpreter or translator. The goal is a text that gives a reader without the original image the same conditional understanding, including what the plotted thermodynamics cannot prove about real hardware.
The short answer: preserve coordinates, species, conditions and uncertainty
A faithful translation states what is on the horizontal and vertical axes, specifies the electrochemical reference where known, identifies each labelled stable species, and uses conditional language for material behaviour. If the chart shows a solid oxide field, say that the oxide is thermodynamically stable in that field; do not silently upgrade it to a guarantee of long-term protection. If the point lies on or close to a boundary, describe the uncertainty rather than pretending the state is unambiguous.
A potential–pH map is not a photograph
A Pourbaix diagram is assembled from equilibrium relationships. The coloured or outlined regions represent conditions under which selected species have favourable thermodynamic stability, not an image of a real surface at that moment. A reader may encounter several competing forms of the same element on one chart.
Translate the explanatory caption as a model-based statement: the diagram predicts predominant equilibrium species for defined conditions. Do not say that the diagram has observed rust forming or measured the thickness of a film. Keep theoretical inference separate from experimental evidence.
When explaining the graphic aloud, identify the material and solution first. Then describe one coordinate and the stable label found at that location. This forces the listener to understand the map as a conditional representation, rather than a forecast with unconditional certainty.
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Horizontal axis: pH rather than acidity by itself
The horizontal coordinate is commonly pH, which increases toward more alkaline conditions. Low pH is acidic; high pH is basic or alkaline. A common language trap is the phrase more acidic, which means a lower numerical pH, not movement to the right on a conventional scale.
A sentence about a point moving right should say that the pH increases, provided the original axis runs from low to high. Resist substituting acidity rises for pH rises. If an unusual figure reverses the horizontal direction, report the plotted direction instead of assuming the standard layout.
To check a translated description, ask a reader to locate pH 3 and pH 11 and name which is more acidic. If the explanation puts strong acid on the high-pH side, repair the language before interpreting any stability region.
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Vertical axis: electrode potential
The vertical coordinate normally represents an electrode potential, often in volts. A higher plotted potential is generally more oxidising relative to the specified reference. This is not the same as a battery’s terminal voltage, a universal absolute energy or an unqualified positive or negative charge.
Include the potential reference if the graph gives one, such as SHE, RHE or a named reference electrode. Two figures with identical numbers on the vertical axis can denote different physical conditions if their reference conventions differ; translating only the word voltage discards that qualification.
Read the axis as a complete unit phrase, for example electrode potential in volts versus the standard hydrogen electrode. Ask whether a quoted numerical potential can be traced to that phrase. Without a reference, a comparison between independent figures may be unsafe.
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SHE, RHE and other reference scales
SHE abbreviates standard hydrogen electrode; RHE refers to reversible hydrogen electrode. Reference conventions matter because translating a potential value as though it were on another scale changes its relationship to equilibrium lines. The conversion may depend on pH, temperature and reference conditions.
Do not turn a labelled V versus SHE into V versus RHE while preserving the same number. A technical reader must be able to locate the point on the specified chart. Where a manuscript switches reference scales, reproduce the authors’ actual conversion and identify its assumptions.
A good bilingual glossary expands each abbreviation once and retains the abbreviation thereafter. A separate note can explain that electrode potentials are comparative measurements, but it should not improvise an arithmetic conversion from incomplete metadata.
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Immunity is an equilibrium domain
An immunity region means the metallic form is thermodynamically stable against the oxidation reaction considered in the diagram. In ordinary language immunity can sound biological or absolute, as if the object can never deteriorate. That implication is not part of the map.
Use metal immunity or thermodynamic immunity when the target language requires qualification. Explain that the region describes a free-energy preference under specified aqueous conditions. Mechanical wear, other reactions and environmental changes lie outside that simple label.
For verification, translate one sample statement and reverse-translate it: at this potential and pH, the elemental metal is the stable represented species. A reverse translation saying the metal is permanently indestructible has added a claim.
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Corrosion fields show soluble products
A corrosion field commonly contains dissolved ionic species of the material. Their presence signals that dissolution is thermodynamically favoured in the equilibrium model. It does not establish the mass of metal lost in one hour or the service life of an engineering component.
Translate corrosion possible or dissolved species stable rather than instant destruction. Keep aqueous state labels such as aq when present, because Fe²⁺(aq) and a solid iron oxide are not interchangeable. Be careful when a language lacks an ordinary adjective precisely corresponding to aqueous.
A quick test is to ask what the plot measured. If a caption asserts a corrosion current, rate in millimetres per year or time to failure without supplementary experiments, the translation has wandered beyond what the potential–pH diagram supplies.
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Passivation is not a universal protective promise
Passivation fields denote conditions in which an oxide or hydroxide phase is stable. Whether the film actually protects a surface depends on continuity, porosity, adherence, mechanical damage and transport of corrosive species. A stable film can be too porous or disrupted to prevent attack.
Translate passive region as a potential for passive-film stability rather than a guarantee of corrosion-free operation. Distinguish a stable solid compound from an effective passivating barrier. These ideas often share a related word in everyday speech but are technically separate.
For a reader-facing caption, add an explicit limit: the diagram does not evaluate film quality or corrosion kinetics. This single sentence prevents a learner from treating a stability field as a warranty for equipment.
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The species printed inside a field matters
A region may be labelled with an elemental metal, a cation, an oxide, a hydroxide or a complex ion. Each formula identifies a chemical entity. Subscripts record composition, superscripts record charge and oxidation-related notation can separate species that sound similar when spoken.
Maintain chemical formulas exactly unless a notation error is demonstrably present in the source and is documented. Translate the surrounding descriptive term, not the atom counts or charge marks. A missing superscript can convert an ionic species into a misleading chemical claim.
Test the text by reading each label against its source formula, including oxidation state and physical state. A second reviewer can mark differences character by character before evaluating fluency or elegance.
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Oxidation states are not typographical decoration
Iron represented as Fe²⁺ differs chemically from Fe³⁺. Another oxidation state may occupy a different part of the equilibrium map. In ordinary writing a lost plus sign looks small; in electrochemistry it changes the identity of the species and potentially the boundary interpretation.
Use typography that preserves superscripts or an accessible plain-text equivalent such as Fe(II) and Fe(III), with the meaning checked against context. Avoid ambiguities between a positive ion’s charge and a positive electrode potential, which are not the same quantity.
A useful editorial check searches the completed article for every species identifier. Compare the symbols and full names with the source once more after export to the content-management system, because rich-text copying can strip raised characters.
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Solid phases and aqueous phases cannot be merged
Fe₂O₃(s), Fe(OH)₂(s) and Fe²⁺(aq) describe different physical states and may have different roles in corrosion. A reader can understand a boundary only when the competing states remain distinct. A sentence saying all are just iron compounds loses the mechanism.
Translate solid, dissolved, precipitated and aqueous with consistent terms. A solid phase represented on the chart need not mean that a mechanically protective coating has formed. Likewise, a stable dissolved ion does not specify how rapidly it leaves the surface.
Use a two-column annotation in working notes, separating formula from physical state, then check both in the translated caption. Even without publishing a table, this preparation protects meaning and supports an accessible prose version.
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Boundary lines describe equilibrium coexistence
The line between two fields represents a set of conditions at which specified species are at equilibrium under the model. It does not mean a physical wall, an instantaneous switching mechanism or a measurement of how far the material has travelled.
Render boundary as equilibrium boundary or line of phase predominance when appropriate, while preserving the particular convention of the figure. If a source calls it a transition, ensure the reader understands that kinetic delays and metastability may complicate observed behaviour.
An accurate sentence says that increasing potential can move the operating point across the boundary into the other species’ thermodynamic domain. An inaccurate one says that the material must transform immediately the instant the line is crossed.
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Horizontal lines have a chemical explanation
A horizontal equilibrium boundary is independent of pH within the model and conditions represented, often because the balanced reaction involves electron transfer without an explicit proton term. Its location is determined by the relevant redox equilibrium and participating species activities.
Do not translate horizontal as chemically constant in every possible solution. The line is horizontal in the coordinates and under the assumptions of this chart. A different chemical system or equilibrium convention may move it, even if its shape remains flat.
A clear description is: this equilibrium potential does not change with pH on the displayed axis. A complete caption should identify the two fields it separates, not merely describe the line’s geometry.
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Vertical lines track acid–base or solubility equilibria
A vertical boundary is independent of potential in the depicted equilibrium relationship, often reflecting an acid–base or dissolution–precipitation balance without electron transfer. The constant pH coordinate can be misread as a reaction that happens only at a particular voltage.
Explain that a vertical line occurs at approximately the same pH across the displayed potential range for the equilibrium represented. Do not say that the line proves oxidation is impossible elsewhere. It distinguishes the phase or dissolved-species regions specified by the plotted model.
During verification, describe an illustrative motion from pH 4 to pH 9 while keeping potential fixed. The translation should make it clear that the point moves horizontally and may cross a pH-governed boundary.
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Sloping lines carry a coupled dependence
Diagonal boundaries often represent equilibria where both electrons and protons occur in the balanced reaction. The slope depends on reaction stoichiometry, temperature and conditions. The Nernst relation is the basis, but not every sloping line has the same numerical gradient.
Do not replace a source-specific gradient with a memorised value. If a chart uses a particular species pair, the number of electrons and protons changes the relationship between potential and pH. Translate the shape and conditional nature before attempting an equation.
Ask the reviewer to identify the fields on either side and the direction in which the potential changes as pH increases. If the translated sentence reverses the incline, it can change which region contains a proposed operating point.
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The water stability limits are contextual
Many Pourbaix diagrams include approximate thermodynamic lines for hydrogen evolution and oxygen evolution. These are useful reference boundaries for aqueous electrochemistry, not laboratory proof that gas forms immediately wherever a point lies beyond them.
Label the two water-related equilibria according to the source and preserve whether the diagram is plotted versus SHE or another reference. Overpotential and reaction kinetics mean the observed onset of gas evolution can differ from the equilibrium line.
When explaining the chart to new learners, say that the lines indicate where hydrogen or oxygen evolution is thermodynamically possible under the stated assumptions. Do not represent them as universal instrumental cutoffs.
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Temperature is part of the model
Thermodynamic constants and Nernst slopes depend on temperature. Many standard diagrams use 25 degrees Celsius, but that cannot be assumed for a figure produced at another temperature. Industrial systems may operate far from laboratory ambient conditions.
If the temperature is stated, preserve it with its unit. If absent, do not invent a standard condition in the published paraphrase. A translated caption should not silently import numerical line values from an unrelated room-temperature example.
Check that a converted temperature is mathematically consistent. For explanation, it is safer to quote the original unit and provide a separately verified conversion than to approximate a number and imply the diagram was computed using it.
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Activities and concentration thresholds move boundaries
A plot may assume specific activities of aqueous ions, sometimes using a nominal very low dissolved concentration to establish a corrosion-field boundary. Altering that assumption can change the size and location of some fields. A threshold is a modelling convention, not a universal legal safety limit.
Translate activity and concentration separately when the source distinguishes them. Activity is a thermodynamic effective concentration affected by interactions; a concentration value alone may not fully describe it. Preserve powers of ten and units in every caption.
For a worked review, compare two sources that use different dissolved-ion activities. A correct translation will state that they are not directly interchangeable maps, even if the same metal appears in both titles.
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Complexing agents alter the chemistry
Chloride, carbonate and other ligands can change which dissolved or solid species are stable. A simplified metal–water diagram may omit such interactions. The resulting regional description can be useful for introductory reasoning without predicting every industrial electrolyte.
If a source says an idealised metal–water system, retain that restriction. Do not extend a passive field to an aggressive chloride-containing solution without an explicit multi-component model or experiment. A translator should resist smoothing away qualifying chemistry.
In practical use, add a provenance sentence naming the electrolyte and whether complexes were included. Where the methods section is unavailable, mark the mechanism beyond the diagram’s scope rather than guessing.
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An operating point has two coordinates
A dot, crosshair or marker on a Pourbaix diagram represents a chosen pH and potential. Its meaning is determined by both coordinates together. Looking only at pH can suggest a passive region that the point does not occupy at the plotted potential.
A translated statement should locate the operating point as, for example, at the indicated pH and electrode potential, inside the labelled oxide-stability region. Avoid converting a two-dimensional condition into a statement about acidity alone.
Read the point, read the legend and then identify its surrounding field. If the marker is on a boundary or hidden by a wide plotted line, record that ambiguity. The physical thickness of a printed line is not measured uncertainty.
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A movement across the diagram is conditional
Arrows may show a change in solution acidity, applied potential or both. The direction of the arrow is not necessarily the direction of a chemical reaction; it may simply represent changing experimental conditions. A sideways movement changes pH, while a vertical movement changes potential.
When translating an arrow caption, write what parameter changed and what was held fixed if known. Do not say that the metal travelled through a chemical process merely because a graphical path crosses two coloured fields.
An effective test asks whether a reader could reconstruct the arrow on blank axes. If the description says the system becomes more oxidising when only the pH was increased, the translation has added an unjustified interpretation.
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Figures may reverse or crop axes
Some published charts display an unusual vertical range, crop water lines or place annotations that visually obscure the axis. Formatting conventions are common but never stronger evidence than the actual labels printed in the source.
Inspect minimum and maximum tick labels before writing up, down, left or right. If a figure reverses the order, say how the plotted values change rather than assuming that higher or lower positions imply the conventional values.
For accessibility, describe physical screen position and the value trend separately: pH increases from left to right, or potential decreases upward if the actual chart shows that. This prevents a visually accurate translation from becoming chemically wrong.
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Colours need a legend and text alternatives
Red, green and blue fields are often introduced for readability, not as universal chemical codes. A green field on one figure might represent oxide stability, while another author assigns green to a dissolved species. Colour alone cannot define safety.
Translate each legend entry and state the chemical label in text. For colour-blind readers and monochrome printing, describe the map by coordinates and region names. Avoid calling a zone safe solely because it is displayed in a calming colour.
An accessible caption names the relevant fields and their positions relative to boundary lines. It should remain intelligible when all colour is removed from the original image.
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Do not confuse potential with current
Pourbaix diagrams are potential–pH equilibrium representations; they do not ordinarily plot current density. A nearby corrosion paper may also contain Tafel or polarisation graphs, which use current to analyse kinetics. Mixing them destroys the intended scientific contrast.
Keep units and x–y labels attached to each figure. If the y-axis is potential in volts, do not switch to current in amperes merely because the surrounding article discusses electrochemical testing. Consider cross-referencing kinetic plots without merging their claims.
A basic audit can search for ampere, current density and corrosion rate in the draft. Any statement treating those as quantities measured by the Pourbaix diagram should be removed or carefully attributed to independent data.
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Thermodynamics and kinetics answer different questions
Thermodynamics indicates whether a transformation is energetically favoured at equilibrium. Kinetics describes how fast a process proceeds and which pathways or barriers control it. Real corrosion depends on both, alongside environmental transport and surface condition.
Translate possible, favoured and stable with the source’s level of confidence. Avoid verbs that imply measured speed. When juxtaposing Pourbaix and Tafel information, preserve a clear boundary between expected stable species and experimentally inferred reaction rates.
A teaching exercise is to have learners write two sentences: one describing a chart’s stability field, another describing a separately measured rate. They should be able to identify exactly which instrument or model supports each claim.
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Passivity may fail locally
An oxide can be stable by bulk thermodynamics while a surface experiences local breakdown, crevice chemistry, chloride attack or mechanical abrasion. Such failures are important when interpreting engineering applications that extrapolate from an idealised potential–pH chart.
Translate passivity as a material condition, not absolute immunity. If the author uses a phrase such as predicted passive region, retain predicted. Never convert a diagram label into an instruction that a structure is safe without additional evaluation.
The safety check is to ask whether the translated text could be mistaken for permission to ignore inspection or testing. Add the actual limitation clearly: this equilibrium map does not certify field performance.
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Iron, aluminium and zinc differ
The same pH–potential coordinate can fall into different stability domains for different elemental systems. An iron example cannot simply replace an aluminium diagram; some oxides are amphoteric and dissolve under strongly acidic or alkaline conditions.
When reusing an explanation, update every species formula, boundary condition and qualitative description, not just the metal name. A translation based on a wrong example can look technically polished while asserting chemistry that belongs to another material.
For cross-checking, state the source element at the start of the caption. Then verify that every formula in the translated glossary contains the correct element and that the stability narrative follows the actual field labels.
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Comparisons require matched assumptions
Two diagrams can be compared responsibly only after identifying temperature, reference potential, species activities, electrolyte composition and plot ranges. A larger passive region in one source may be partly explained by how the model was set up rather than a universally better material.
The wording should distinguish a comparison of plotted thermodynamic domains from a comparison of tested corrosion resistance. Readers making design decisions need that difference. A translated claim that one alloy always outlasts another exceeds the figure.
When an article compares panels, repeat or cross-reference the assumptions in each panel’s caption. The reader should be able to discover whether the same axes, units and conditions are used.
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Captions should identify model inputs
A useful scientific caption names the element, medium, plotted variables, temperature, activity convention, main phase fields and line styles. Not all details fit into one sentence, so a short caption plus explanatory paragraph is often clearer.
Translate the full legend before paraphrasing findings. A caption that skips a dashed-line explanation may leave water stability limits indistinguishable from metal-species boundaries. This is an error of information architecture rather than grammar alone.
A concise reading order is title, axes, reference, species, boundaries, operating point, limitations. Apply it consistently in multilingual classroom notes and technical documentation, while leaving out no source-provided condition.
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Alternative text should explain relationships
Useful image alternatives describe the relationships that enable the reader to infer meaning, not every coloured pixel. Mention pH direction, potential reference, major regions and the location of any highlighted operating point. A detailed figure can also justify a nearby text explanation.
Do not invent an image or substitute a generic corrosion photograph for a chart. If the graphic cannot be included, a precise prose description with qualified examples is more honest. Maintain the distinction between observable labels and interpretive conclusions.
An accessibility review should let a reader who cannot see the diagram answer three questions: what variables are plotted, which species dominates at the discussed coordinate, and what the model cannot determine.
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Handle multilingual names and abbreviations consistently
The terms Pourbaix diagram, E–pH diagram, potential–pH diagram, corrosion, immunity and passivation have specialist meanings. Their closest everyday-language equivalents may be misleading. A terminology note can preserve the recognised English expression alongside a clear target-language definition.
A first mention can supply a translated name followed by the standard abbreviation in parentheses. In later paragraphs reuse the same expression. Do not alternate casually between stable, safe, passive and immune, because they do not describe the same status.
Ask a bilingual reviewer to explain the difference between an immunity field and a passivation field without referring to their colours. If the target terms produce the same answer, the glossary needs sharper definitions.
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Numerical and typographic verification is a separate pass
Decimals, superscripts, minus signs, inequalities and chemical charges survive poorly when figures are retyped. A minus sign before a potential and a superscript charge after an ion perform entirely different jobs; reversing either may relocate the interpreted condition.
Perform a technical proofread after the language edit. Check every number, axis limit, variable, chemical formula, subscript and reference label. Formatting can change during translation memory export or when pasting into an editor, so inspect the actual rendered text.
One effective practice is to isolate the mathematical and chemical tokens during proofreading. If they are identical to the verified source and the prose maintains the same relationships, the risk of an elegant but scientifically wrong translation falls.
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Use uncertainty where boundaries are approximate
Computed boundaries can depend on database selection and activity assumptions, while a printed figure may have limited resolution. A point drawn very close to a boundary should not be assigned to one stable phase with unrealistic precision.
Say near the boundary or under these model conditions where the original warrants it. Do not turn a diagram’s approximate label into a measured threshold with extra decimal places. When comparing sources, acknowledge model differences rather than forcing all maps to coincide.
Ask whether a precise numerical crossing was actually calculated or merely read from a small figure. If it was estimated visually, retain an appropriately qualified description in the translated text.
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A decision-ready explanation still requires evidence
Pourbaix diagrams inform material selection, experiment planning and corrosion reasoning, but they do not replace exposure testing, electrochemical measurements or inspection. Translation becomes risky when a teaching chart is promoted as proof of long-term industrial performance.
Distinguish descriptive education from engineering certification. A phrase such as potentially stable oxide is justified by the figure; guaranteed noncorrosive pipeline is not. Keep recommendations conditional on independent performance data and applicable standards.
Before publishing, check that readers are told the chart’s limitations and know where experimental corroboration would come from. This is especially important when the text will circulate without the original academic paper.
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Worked interpretation: reconstruct one chart in ordinary language
Imagine an educational iron–water potential–pH diagram in which the horizontal scale reads low pH at the left and higher pH at the right. The vertical scale reads electrode potential versus a stated reference. A labelled metallic iron field occupies one part of the map, dissolved iron species another, and solid iron oxide regions a further part. Begin by describing these observable labels. Only after that should you say which field a marked operating point occupies. If a point sits within a solid-oxide domain, the justified inference is that the plotted oxide is thermodynamically favoured for the specified conditions. Whether that oxide actually forms a dense protective film is a separate experimental question.
Now imagine rewriting the same chart for readers who do not know the specialist vocabulary. A poor summary might say that iron is safe in the green zone and will dissolve instantly in the red zone. A faithful summary instead reads: the diagram identifies conditions favouring metallic iron, dissolved species or solid corrosion products. Green and red are colours chosen by the figure maker, not universal electrochemical classifications. Rates and protective quality cannot be read from the equilibrium boundaries. The second explanation is slightly longer, but it preserves the actual evidence and gives readers a way to reason responsibly.
Translation checklist for readers, tutors and editors
Identify the element or alloy and aqueous chemistry before looking for target-language synonyms. This is a practical editorial checkpoint: the target text should help a reader reconstruct the same scientific meaning rather than simply recognise familiar terminology.
Copy the pH axis and the potential axis, including directions, units and electrode reference. This is a practical editorial checkpoint: the target text should help a reader reconstruct the same scientific meaning rather than simply recognise familiar terminology.
Record temperature, activity conventions, legend symbols and named species as source facts. This is a practical editorial checkpoint: the target text should help a reader reconstruct the same scientific meaning rather than simply recognise familiar terminology.
Distinguish dissolved ions, solid films and elemental metal in both language and formula. This is a practical editorial checkpoint: the target text should help a reader reconstruct the same scientific meaning rather than simply recognise familiar terminology.
Treat equilibrium lines as boundaries between modelled stable species, not measured rates. This is a practical editorial checkpoint: the target text should help a reader reconstruct the same scientific meaning rather than simply recognise familiar terminology.
Mark the operating point and verify it has two coordinates and a specific stability field. This is a practical editorial checkpoint: the target text should help a reader reconstruct the same scientific meaning rather than simply recognise familiar terminology.
Check whether the source includes water-stability lines and explains their assumptions. This is a practical editorial checkpoint: the target text should help a reader reconstruct the same scientific meaning rather than simply recognise familiar terminology.
Retain conditional words when describing corrosion, immunity and potential passivation. This is a practical editorial checkpoint: the target text should help a reader reconstruct the same scientific meaning rather than simply recognise familiar terminology.
Proofread oxidation-state marks, charges, decimals and negative potential signs separately. This is a practical editorial checkpoint: the target text should help a reader reconstruct the same scientific meaning rather than simply recognise familiar terminology.
Include a prose alternative explaining the chart without relying on colours. This is a practical editorial checkpoint: the target text should help a reader reconstruct the same scientific meaning rather than simply recognise familiar terminology.
Compare each target sentence with the original and identify what evidence supports it. This is a practical editorial checkpoint: the target text should help a reader reconstruct the same scientific meaning rather than simply recognise familiar terminology.
Have a technically informed reviewer check any decision-relevant engineering claim. This is a practical editorial checkpoint: the target text should help a reader reconstruct the same scientific meaning rather than simply recognise familiar terminology.
Questions people ask about translating Pourbaix diagrams
What does a Pourbaix diagram show?
It shows thermodynamically predominant species for an element or chemical system as a function of pH and electrode potential under stated assumptions. It can explain the possibility of immunity, dissolution or oxide stability, but does not measure corrosion speed. For multilingual use, retain each explicit condition in the target wording and give the reader a way to verify the claim against the plotted labels and the source methods.
Does green always mean a safe region?
No. Colours depend on the author. Read the field formula and the legend. Even a region showing a stable oxide does not automatically establish that the film provides reliable protection in real service. For multilingual use, retain each explicit condition in the target wording and give the reader a way to verify the claim against the plotted labels and the source methods.
Can a chart predict the rate of rust formation?
No. The thermodynamic model does not directly contain corrosion current, transport rates, film defects or mechanical damage. Use experimental kinetics and exposure evidence when rate matters. For multilingual use, retain each explicit condition in the target wording and give the reader a way to verify the claim against the plotted labels and the source methods.
Why must I keep the reference electrode?
A numerical potential only has a defined electrochemical meaning relative to a reference convention. Omitting SHE, RHE or another stated reference can change where the reader thinks a condition lies on the map. For multilingual use, retain each explicit condition in the target wording and give the reader a way to verify the claim against the plotted labels and the source methods.
How should I translate a sloping boundary?
Identify the species on either side, note that potential changes with pH along that equilibrium and retain the source conditions. Avoid assigning a universal gradient unless the balanced reaction and temperature justify it. For multilingual use, retain each explicit condition in the target wording and give the reader a way to verify the claim against the plotted labels and the source methods.
Is passivation the same as immunity?
No. Immunity refers to thermodynamic stability of the metallic form in the model. Passivation refers to conditions favouring a solid surface compound, which may protect if its physical and chemical properties support a barrier. For multilingual use, retain each explicit condition in the target wording and give the reader a way to verify the claim against the plotted labels and the source methods.
Can I compare two diagrams from different papers?
Yes, but first align reference potential, temperature, ion activity, species assumptions and electrolyte chemistry. Without that comparison, an apparent change in boundary position might come from different modelling inputs. For multilingual use, retain each explicit condition in the target wording and give the reader a way to verify the claim against the plotted labels and the source methods.
What should accessible alternative text contain?
Name the two axes and their direction, the important phase fields, the water lines if relevant, and any highlighted point. The prose should communicate the scientific relationship without depending on colours alone. For multilingual use, retain each explicit condition in the target wording and give the reader a way to verify the claim against the plotted labels and the source methods.
Connected learning: corrosion, charts, chemistry and translation
For the next stage of learning, compare equilibrium maps with experimental electrochemistry in eduKateSG’s Tafel plots and polarisation curves guide and cyclic voltammogram guide. These graphs answer different questions and should not be merged during translation. The Nyquist plot guide covers a further distinction between impedance and reaction thermodynamics.
Readers building English scientific vocabulary can connect chart-reading practice to scientific spectrum interpretation and to battery charge–discharge curve interpretation. The recurring habit is transferable: identify variables, reconstruct relationships, explain what the data support and verify the translation independently.
For technical grounding, see the open research discussion of potential–pH diagrams and corrosion of multicomponent alloys and the Google Search Central guidance on useful educational content. Each source plays a different role: scientific reference for equilibrium methods and editorial guidance for writing that genuinely answers the reader’s question.
The final principle
Good translation of a Pourbaix diagram is an exercise in protecting conditions. The reader must know which system is plotted, what the axes mean, which species the regions represent and why an equilibrium stability field is not the same as a guaranteed engineering outcome. Once that discipline is in place, the specialised words become easier to translate because the scientific relationships no longer depend on a guess. A trustworthy explanation can be read, checked and taught without changing what the original graphic means.