Lead reacts with oxygen in air, water under certain conditions, most acids, halogens like chlorine, and sulfur-containing gases, but it does so more slowly than many other common metals. A thin oxide layer forms almost immediately when lead is exposed to air, and that layer then acts as a shield that slows further attack. This self-protecting behavior is what makes lead useful in pipes, batteries, and roofing, but it also means the story of lead’s reactivity is really a story about when that protective coating holds up and when it breaks down.
How Lead Reacts with Air
When a fresh lead surface meets oxygen at room temperature, a thin film of lead oxide (PbO) forms quickly. Research using surface-analysis techniques shows that this oxide grows laterally across the metal as a film roughly two monolayers thick, after which oxygen uptake slows dramatically.1Surface Science. A comparison between the oxidation of bulk lead and that of lead deposits on Au(111): An auger study In practical terms, a freshly cut piece of lead will lose its bright metallic shine within minutes and turn a dull grey. That grey coating is the oxide, and once it is in place, the metal underneath stays largely protected.
The initial oxidation is not entirely uniform. Studies of lead crystal surfaces found that the oxide nucleates at surface impurities and then spreads outward in an autocatalytic process, meaning the growing edge of the oxide film itself speeds up the reaction nearby.2PubMed. Autocatalytic oxidation of lead crystallite surfaces The oxide that forms under ordinary conditions is PbO, which exists in two crystal forms: a red-orange variety called litharge and a yellow one called massicot. If lead is heated in air to higher temperatures, further oxidation can produce the bright red compound known as red lead (Pb₃O₄), historically used as a pigment and a primer coat on iron and steel. Under still more aggressive conditions, lead dioxide (PbO₂), a dark brown compound, can also form.
Over longer periods outdoors, carbon dioxide in the atmosphere reacts with the surface oxide to produce lead carbonate, and moisture promotes the formation of a mixed carbonate-hydroxide mineral called hydrocerussite. This carbonate patina is the whitish crust you see on old lead flashings on roofs or on centuries-old lead statues. It is denser and less porous than the initial oxide, so it actually improves the metal’s long-term corrosion resistance. The interplay between PbO, lead carbonate, and hydrocerussite depends on humidity and the local concentration of CO₂; under normal atmospheric conditions, hydrocerussite is the thermodynamically favored product.3Journal of Crystal Growth. Crystal growth of lead carbonates: Influence of the medium and relationship between structure and habit
Lead and Water
Pure water by itself barely attacks lead. The metal sits below hydrogen in the reactivity series, so it does not displace hydrogen from water the way sodium or even iron would. In theory, lead should be almost inert in clean, neutral water. The trouble is that real-world water is never pure. Dissolved oxygen, chlorine added during disinfection, natural organic matter, and shifts in pH all change the equation.
When lead plumbing or lead solder contacts chlorinated drinking water, an electrochemical process begins. Lead atoms lose electrons and become dissolved lead ions (Pb²⁺). Those ions can then react with other substances in the water to form a mix of corrosion products on the pipe’s inner surface. In chlorinated water, the corrosion products tend to include lead oxides, lead carbonates, and sometimes chloride-containing compounds. Studies of lead pipes in different municipal water systems show that the composition of these corrosion scales varies with water chemistry, and the scales can either lock lead in place or periodically release it, depending on how stable the mineral layers are.4PubMed. Influence of drinking water quality on the formation of corrosion scales in lead-bearing drinking water distribution systems
Galvanic corrosion makes the problem worse. When lead is in physical contact with a different metal, such as the brass fittings commonly found in plumbing, the two metals form an electrochemical cell in the presence of water. Lead becomes the anode, meaning it corrodes preferentially. Research on lead-brass junctions in chlorinated water found that dissolved lead ions at these contact points cause a local drop in pH and draw chloride ions toward the corroding surface, accelerating the attack.5PubMed Central. Microelectrode Investigation on the Corrosion Initiation at Lead–Brass Galvanic Interfaces in Chlorinated Drinking Water This is one reason why replacing only part of a lead service line with copper can sometimes make lead exposure worse rather than better: you create a new galvanic couple right at the junction.
Reactions with Strong Mineral Acids
Lead’s behavior with acids is more complicated than you might expect from a textbook list. The outcome depends heavily on which acid you use, because the reaction product can either dissolve away (exposing fresh metal and keeping the reaction going) or form an insoluble coating that shuts the reaction down.
Hydrochloric Acid
Lead dissolves in dilute hydrochloric acid (HCl), releasing hydrogen gas and producing lead chloride (PbCl₂). But lead chloride has limited solubility in water. As the reaction proceeds, a layer of PbCl₂ crystals builds up on the metal surface and passivates it, slowing and eventually stopping further dissolution. Electrochemical studies found that in HCl concentrations below about 0.4 molar, the rate-limiting step is how fast chloride ions can diffuse to the surface to form that passivating layer.6Canadian Journal of Chemistry. Electrochemical Behavior of the Lead Electrode in HCl and NaCl Aqueous Electrolytes At intermediate concentrations, around 0.7 molar, the system oscillates between passivation and dissolution, because the PbCl₂ layer forms, partially dissolves, reforms, and so on.7Corrosion Science. Kinetics of anodic behaviour of Pb in HCl solutions At very high HCl concentrations, lead chloride’s solubility actually increases because it forms soluble chloro-complexes, so the protective layer cannot form and the metal dissolves more readily.
Sulfuric Acid
Dilute sulfuric acid attacks lead initially, but the product is lead sulfate (PbSO₄), which is extremely insoluble. The sulfate layer clogs the surface so effectively that the reaction essentially stops. This is why lead has been used for centuries to line sulfuric acid storage tanks and why it works as the electrode material in car batteries. Electrochemical research on lead in concentrated (35%) sulfuric acid showed that the passivation process involves an initial thin barrier film of lead sulfate through which lead ions migrate, followed by precipitation of a thicker, more crystalline outer layer.8Corrosion Science. Electronic and optical properties of passive film: A conductive film model for the lead anode in sulfuric acid Ellipsometric studies confirmed this two-layer structure and showed that the inner layer is somewhat porous, allowing lead ions to seep through and contribute to a coarser outer crust.9Electrochimica Acta. In-situ ellipsometric study of lead sulfate film electroformation on lead in a sulfuric acid solution In hot, concentrated sulfuric acid the sulfate layer eventually breaks down and lead dissolves, but under normal industrial conditions the passivation holds.
Nitric Acid
Nitric acid is the classic solvent for lead. Unlike HCl and H₂SO₄, the product here is lead nitrate, which is highly soluble. No protective layer forms, so the metal keeps dissolving. Dilute nitric acid attacks lead briskly, producing lead nitrate and releasing nitrogen oxide gases. As the acid concentration increases, the dissolution rate climbs almost linearly, but at high concentrations an interesting reversal occurs: a protective layer of lead dioxide (PbO₂) forms on the surface and the reaction slows down.10Surface and Coatings Technology. Study of the dissolution of lead in nitric acid by the thermometric technique So even with the one acid that usually defeats lead’s defenses, concentrated conditions can trigger a different passivation mechanism.
How Organic Acids Attack Lead
You do not need a strong mineral acid to corrode lead. Weak organic acids, the kind found in food and everyday life, are surprisingly effective. Acetic acid (vinegar), citric acid (citrus fruits and tomatoes), and lactic acid (fermented foods) all react with lead, and this has been both exploited and feared for centuries.
The most famous deliberate use is the centuries-old “Dutch process” for making lead white pigment. Strips of metallic lead were stacked in clay pots above a pool of vinegar, inside a shed packed with fermenting manure. The manure provided heat and CO₂, the vinegar supplied acetic acid vapor, and together with oxygen and moisture they slowly converted the lead surface into a mixture of lead carbonate and basic lead carbonate, the brilliant white pigment prized by painters from antiquity through the 1800s.11Corrosion Science. Synthesizing lead white pigments by lead corrosion: New insights into the ancient manufacturing processes The process worked precisely because acetic acid vapor is aggressive enough to break down lead’s protective oxide, letting oxygen and CO₂ reach the fresh metal beneath.
The same chemistry creates real health hazards when acidic foods come into contact with lead-glazed pottery. A study of traditional glazed cookware sold at the Mexico-US border found that cooking acidic food in those vessels produced a median lead concentration in the food of about 103 mg/kg, roughly nine times the level measured when nonacidic food was cooked in the same pots.12PubMed. Enhanced Leaching of Soluble Lead by Cooking Acidic Food in Glazed Pottery Sold at the Mexico-US Border Research on Egyptian ceramicware confirmed the pattern: acetic acid solutions leached visible amounts of lead from glazed bowls, and the amount of lead transferred into salsa cooked by traditional stovetop methods was higher than in microwave-cooked batches, likely because the longer contact time and higher temperatures in conventional cooking promoted more leaching.13Food Chemistry. Release of lead from glaze-ceramicware into foods cooked by open flame and microwave
Temperature and acidity both matter in a predictable way. Extraction experiments on glazed ceramic tiles using acetic, citric, and lactic acid at different temperatures found that lead leaching increased with temperature and decreased with rising pH (meaning more acidic solutions pulled out more lead).14Mathematical Problems in Engineering. Migration of Toxic Metals from Ceramic Food Packaging Materials into Acid Food Simulants The practical takeaway: if you own decorative or imported pottery that might contain lead glaze, avoid storing or cooking acidic foods like tomato sauce, citrus marinades, or vinegar-based dressings in it.
Lead and Halogens
Lead reacts directly with halogen gases. Chlorine gas, for instance, attacks metallic lead to produce lead chloride (PbCl₂). The reaction kinetics follow a two-stage pattern: an initial fast phase governed by the surface reaction, then a slower phase in which diffusion through the growing PbCl₂ layer becomes the bottleneck.15Journal of Solid State Chemistry. The reaction between solid lead and chlorine gas This is essentially the same passivation story seen with HCl: lead chloride builds up and progressively shields the metal, though with pure chlorine gas the initial attack is more vigorous than in dilute acid solution.
Fluorine, bromine, and iodine all react with lead as well, producing lead fluoride, lead bromide, and lead iodide respectively. Lead iodide is notable for its vivid yellow color and its role in modern perovskite solar cells, where it serves as a precursor material. Lead fluoride has uses in specialized optics because of its transparency to infrared light.
Lead and Sulfur Compounds
Anyone who has looked at old oil paintings knows what sulfur does to lead. Lead-based pigments, especially lead white, react with hydrogen sulfide (H₂S) in the air to form lead sulfide (PbS), the mineral galena, which is jet black. This reaction has been responsible for the darkening of countless historical artworks. A study of pigment blackening confirmed that lead-containing pigments reacted quickly with H₂S, with only a few exceptions, to produce galena.16Journal of Cultural Heritage. The role of H2S in pigment blackening The same reaction happens on lead flashings and ornamental lead exposed to polluted urban air, where trace levels of H₂S from vehicle exhaust and industrial emissions gradually darken the surface.
Conservators have developed treatments using hydrogen peroxide to convert the black PbS back to white lead sulfate, partially reversing the damage. But prevention is more effective than cure, and modern museums control sulfur-containing pollutants in their galleries to slow this reaction.
Why Lead Works in Batteries
Lead-acid batteries, the kind under almost every car hood, exist because of the very reactions described above. The battery exploits the fact that both lead and lead dioxide react with sulfuric acid to form lead sulfate, and that the reaction is reversible when you push electric current through the system. During discharge, the metallic lead negative plate and the lead dioxide positive plate both convert to lead sulfate, consuming sulfuric acid and releasing electrical energy. During charging, an external voltage reverses the process: lead sulfate on the negative plate is reduced back to metallic lead, and lead sulfate on the positive plate is oxidized back to lead dioxide.
Research into the mechanism shows that both the discharge and the charge half-reactions proceed through dissolution-precipitation steps. Lead atoms do not transform directly into lead sulfate crystals on the surface. Instead, lead dissolves as Pb²⁺ ions, those ions migrate a short distance through the electrolyte, and then PbSO₄ precipitates.17Journal of Power Sources. Dissolution and precipitation reactions of lead sulfate in positive and negative electrodes in lead acid battery On charging, the reverse happens: lead sulfate dissolves, and either metallic lead or lead dioxide re-precipitates depending on which electrode you are looking at. The passivation that would be a problem in a chemical reactor is actually what makes the battery work: the PbSO₄ layer is porous enough to allow ionic transport but stable enough to prevent the electrodes from crumbling. When the sulfate layer grows too thick or too dense, the battery loses capacity, which is the basic mechanism behind battery aging and sulfation.
Controlling Lead Corrosion in Drinking Water
Since lead’s reactivity with water is the root cause of lead contamination in drinking water, water utilities use chemical treatments designed to encourage the formation of stable, insoluble mineral layers inside lead pipes. The two most common approaches are adjusting the water’s pH and alkalinity to promote lead carbonate scale formation, and adding phosphate-based corrosion inhibitors.
Orthophosphate addition works by reacting with dissolved lead to form lead phosphate minerals, particularly hydroxylpyromorphite, which is extremely insoluble and forms a tight barrier on the pipe wall. Research on early-phase corrosion scale development found that in the presence of orthophosphate, distinctive lead-calcium phosphate minerals formed on the pipe surface, and in systems without free chlorine, hydroxylpyromorphite was identified as a key corrosion product.18PubMed. Early phase effects of silicate and orthophosphate on lead (Pb) corrosion scale development and Pb release This is the same strategy used in Washington, D.C., after a well-publicized lead crisis in the early 2000s, and it has since become standard practice in many water systems serving areas with legacy lead plumbing.
The effectiveness of these treatments depends on maintaining consistent water chemistry. Sudden changes in disinfectant type, pH, or source water can destabilize the protective scale and cause a spike in lead release, as several U.S. cities have learned the hard way. Lead’s reactivity with water is manageable, but only if you respect the chemistry that keeps it in check.
Chelation and Organic Ligands
Lead also reacts with organic molecules that can wrap around the metal ion and hold it in solution, a process called chelation. This matters in both environmental science and medicine. In contaminated soils, natural organic acids like citric acid and synthetic chelators like EDTA can bind dissolved lead and change how it moves through the environment and into plants.
Experiments on fava bean plants grown in lead-contaminated nutrient solutions showed that adding EDTA reduced the amount of lead the plants accumulated in their leaves, in a dose-dependent manner. Citric acid, by contrast, did not significantly change how much lead the plants took up.19Journal of Geochemical Exploration. Effect of organic ligands on lead-induced oxidative damage and enhanced antioxidant defense in the leaves of Vicia faba plants The difference likely comes down to how tightly each molecule binds the lead ion: EDTA forms a very stable complex that keeps lead locked up and less available for root uptake, while citric acid’s grip is weaker.
In medicine, chelation therapy uses drugs like EDTA and succimer (DMSA) to bind lead in the bloodstream and promote its excretion through the kidneys. The principle is the same: a molecule that reacts with lead ions more strongly than the body’s own proteins do can pull lead out of tissues where it is causing harm. Chelation is reserved for cases of significant lead poisoning and is not a substitute for removing the source of exposure, but it illustrates how lead’s affinity for certain organic functional groups can be turned to practical advantage.
Reactions That Darken and Discolor Lead Objects
If you collect antique lead items or maintain old buildings with lead features, the visible changes on the surface tell you which reactions have been at work. A dull grey patina is the oxide layer from air exposure. A white powdery crust is typically lead carbonate or basic lead carbonate, sometimes called white lead. Black tarnish points to lead sulfide from exposure to sulfur-containing gases or pollutants. A greenish tinge on lead near oak timbers usually means acetic acid vapors from the wood have attacked the metal, producing lead acetate or mixed acetate-carbonate corrosion products.
Each of these products has different solubility and toxicity. Lead sulfate and lead carbonate are relatively insoluble and tend to stay put, which limits ongoing exposure. Lead acetate, on the other hand, is quite soluble and has historically been called “sugar of lead” because of its sweet taste, a property that led to widespread accidental poisoning in eras when lead vessels were used for wine and food preparation. Understanding which reaction produced which corrosion product helps conservators, public health investigators, and building managers assess risk and choose appropriate remediation strategies.