Corrosion Inhibitors & Metal Deactivators

Browse CheMost Corrosion Inhibitors & Metal Deactivators

Start with the product family that best matches your formulation target. Each product page goes deeper into the exact grade, properties, and documentation.

Two Jobs: Stop Rust, and Deactivate Metals

“Corrosion inhibitor” and “metal deactivator” are often used loosely, but in a lubricant they solve two distinct problems — and the metal involved decides which you need:

• Rust inhibition — protecting ferrous metals (steel, iron). A corrosion inhibitor lays down a water-repelling barrier film on steel so water and oxygen cannot start the electrochemical rusting reaction. This is the job in metalworking fluids, slushing oils, hydraulic and turbine oils.
• Metal deactivation — protecting (and managing) non-ferrous metals, mainly copper. A metal deactivator forms a film on copper and brass to stop it corroding or staining, and — just as important — it sequesters dissolved copper ions that would otherwise catalyse oil oxidation, gum and deposits. So it protects the metal and the oil.

Most full formulations use both: a rust inhibitor for the steel and a metal deactivator for the copper-containing parts, especially where active-sulfur EP chemistry is present.

Rust Inhibition — Ferrous Metal Protection

Rust is an electrochemical reaction: iron oxidises at the anode while oxygen is reduced at the cathode. The lubricant rust inhibitors used here are mixed organic inhibitors — they adsorb as a monolayer with the polar head anchored to the steel and the oily tail packed outward, forming a barrier that water cannot penetrate. The tighter that film packs, the harder it is to wash off.

CheMost’s rust inhibitors in this range are sodium petroleum sulfonates. Sodium is chosen deliberately: the divalent calcium, magnesium and barium sulfonates are stronger rust preventives in straight oils, but they are detrimental to the stability of soluble-oil emulsions — so the sodium salt is the right choice for water-tolerant and emulsifiable metalworking fluids, where it both inhibits rust and helps emulsify. (For heavy-duty straight slushing and mill oils, the stronger barium and calcium sulfonates live in our rust inhibitors range — overall rust effectiveness runs Na < Mg < Ca < Ba.) Rust performance is validated with standard methods such as ASTM D665 (turbine-oil rust), ASTM D1748 (humidity cabinet) and ASTM D4627 (iron-chip corrosion for water-dilutable fluids).

Metal Deactivation — Copper & Yellow-Metal Protection

Copper, brass and bronze need a different chemistry. A metal deactivator works two ways at once: it forms an inactive film on the metal surface, and it complexes (sequesters) any copper ions that have already dissolved into the oil. That second action matters because dissolved copper is a powerful oxidation catalyst — copper’s complex stability constant (~10¹⁵) is far above other common metals — so deactivating it protects the whole oil from premature oxidation and deposit formation.

The two workhorse chemistries are aromatic triazoles — benzotriazole is the classic copper protectant — and thiadiazoles, which are especially useful for protecting brass and bronze in systems that rely on active-sulfur EP additives. In fact, a metal deactivator is most needed precisely where active sulfur is present, and copper corrosion is checked with the ASTM D130 copper-strip test.

The CheMost Range — How to Choose

Start with the metal you are protecting: steel (rust inhibitor) or copper/yellow metals (metal deactivator).

Rust inhibitors — ferrous, for metalworking & water-tolerant systems

Sodium petroleum sulfonates that inhibit rust on steel and help emulsify — the right family for soluble-oil and semisynthetic metalworking fluids.

Metal deactivators — non-ferrous, for copper & yellow metals

Triazole and thiadiazole chemistries that protect copper and brass and suppress metal-catalysed oxidation.

Treat Rate & Selection Logic

Choosing within this category is not “copper, so add benzotriazole”. The questions that matter:

• Which metal(s)? Steel points to a rust inhibitor; copper/brass/bronze points to a metal deactivator; most oils need both.
• Oil or water-based? Soluble-oil and water-tolerant metalworking fluids need the sodium sulfonate (the divalent salts hurt emulsion stability); straight oils can use stronger barium/calcium rust inhibitors.
• Is active sulfur present? Active-sulfur EP systems make yellow-metal protection essential — budget for a metal deactivator.
• Treat rate. Metal deactivators are low-treat, high-impact (small additions protect copper and the oil); sulfonate rust inhibitors are a much larger component of a soluble-oil concentrate. Exact levels depend on the base stock and the rest of the package.

The test methods and chemistry rankings above are industry-standard references. The right grade, dose and combinations depend on your base stock, metallurgy and targets — CheMost can advise on selection and a starting point on request.

Common Applications

• Metalworking fluids: sodium sulfonate rust protection and emulsification in soluble-oil and semisynthetic fluids; benzotriazole where copper parts are machined.
• Industrial gear & EP oils: metal deactivators protect bronze and brass components where active-sulfur EP additives are used.
• Turbine & hydraulic oils: rust protection of steel plus copper deactivation for long, clean service life.
• Engine & transmission oils: copper/lead bearing protection and oxidation control.
• Greases & fuels: yellow-metal protection and oxidation-catalyst control, including fuel and jet-fuel systems.

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