Rust inhibitors
Temporary rust-preventive formulations, product-specific properties, vapor protection, and the limits of corrosion-test claims.
Tags: chemicals, corrosion, surface-finishing
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Identity and scope
ZERUST’s Axxanol 750 combines a contact oil film with vapor corrosion inhibition in an enclosure. 750-NV is a separate version without VCI. 750 TDS Temporary protection covers iron and steel, and individual multimetal products can name additional substrates. AMPP, What is corrosion?
Compare supplied product, residual film and packaging separately. The protection claim depends on the tested combination.
Rust conversion is a separate function. Cortec describes CorrVerter as a primer that converts a rusted surface into a hydrophobic passive layer for subsequent top coating. That reactive treatment differs from temporary preservation. Synthesis. Neither a rust-removal process nor a complete permanent coating system is defined by the label "rust inhibitor." Cortec, CorrVerter.
Formulation and product distinctions
| Exact product | Supplied form and protective function | Boundary |
|---|---|---|
| Cortec VpCI-377 and VpCI-377 Winterized | Water-based concentrate producing a clear, dry, hydrophobic film for indoor protection. Listed metals include carbon steel, stainless steel, galvanized steel, aluminum, and copper. | Winterized has a water and propylene glycol carrier. The two grades have separate property ranges. PDS, pp. 1 to 2. |
| ZERUST/EXCOR Axxanol 750 | Ready-to-use oil with contact inhibition, a moisture barrier, and vapor corrosion inhibitor chemistry. | VCI protection depends on enclosure. Axxanol 750-NV is a separately named alternative without VCI. Packaging devices are not the supplied oil. TDS, pp. 1 to 2. |
| Cortec VpCI-368 | Solvent-based temporary wax-like coating with multimetal protection. | VpCI-368 M, VpCI-368 D, and CorShield VpCI-368 aerosol are distinct versions. The military qualification claim identifies M. PDS, p. 1. |
| ITW Pro Brands LPS 3 | Wax-base protective coating, sold in aerosol and non-aerosol forms. | US aerosol 00316 differs from non-aerosol 00322, 03128, 00305, and 00355. The TDS also lists Canadian and European product codes. TDS, p. 1. |
Axxanol 750's vapor chemistry migrates to otherwise difficult-to-reach surfaces within enclosed packaging. This supplements its contact film. The TDS declaration limits protection claims to controlled internal testing on contaminant-free substrates and identifies environmental conditions, surface cleanliness, and coating thickness as sources of variation. Axxanol 750 TDS, pp. 1 to 2.
Product properties and measurement bases
These are supplier-reported typical properties, not acceptance limits or operating settings. Missing measurement conditions remain missing.
| Product and source | Reported quantities | Measurement limits |
|---|---|---|
| VpCI-377 | Nonvolatile content 40 to 47%; neat pH 7.5 to 9.5; density 1.04 to 1.10 kg/L. | Nonvolatile percentage basis and density temperature are unstated. Neat pH describes the supplied concentrate. PDS, p. 2. |
| VpCI-377 Winterized | Nonvolatile content 36 to 42%; neat pH 7.8 to 8.9; density 1.05 to 1.10 kg/L. | Separate grade values, with the same missing percentage basis and measurement temperatures. PDS, p. 2. |
| Axxanol 750 | Kinematic viscosity approximately 11.1 cSt at 40°C; VOC 257 g/L by EPA Method 24; flash point 80°C by ASTM D93. | These are product properties. Neither viscosity nor VOC identifies inhibitor activity. TDS, p. 1. |
| VpCI-368 | Volume solids 61%; density 0.91 kg/L; viscosity 2,000 to 5,000 cP; VOC 347 g/L; flash point 70°C. | No viscosity temperature or shear condition, density temperature, VOC method, or flash-point method is stated. PDS, p. 1. |
| LPS 3 non-aerosol, US SDS version 9.27 | Relative density 0.80 to 0.85 with water = 1; viscosity less than 20 cSt; flash point 40°C; volatile component 75% by volume. | Reference temperature, viscosity temperature, and flash-point method are unstated. VOC and supplied pH are unavailable. SDS, section 9. |
Synthesis. cP describes dynamic viscosity and cSt describes kinematic viscosity. Converting between them requires density at the same temperature. A relative density is dimensionless, unlike kg/L. Nonvolatile content, volume solids, volatile volume fraction, and VOC are different quantities. None alone supplies the concentration of corrosion-inhibiting ingredients or the composition of the residual film. A concentrate property cannot be assigned to a working bath or protected part.
The LPS TDS gives aerosol flash point 18°C, relative density 0.87, and VOC 62.8%, with no percentage basis identified for VOC. Its non-aerosol column has different values and no VOC value. These columns cannot be combined into one product profile. LPS 3 TDS, p. 1.
Composition and compatibility limits
The 2025 US LPS 3 non-aerosol SDS identifies light petroleum distillates, propylene glycol monobutyl ether, n-nonane, and Stoddard solvent. Section 3 gives weight ranges and states that specific identity or exact concentration information is withheld as a trade secret. It does not identify the complete protective additive system or assign an inhibition mechanism to every listed ingredient. LPS 3 SDS, section 3.
VpCI-377's PDS describes the product as free of nitrite and phosphate esters. That formulation claim is not a lot assay or a detection limit. The reviewed product documents do not disclose enough chemistry to attribute protection to a particular borate, carboxylate, or amine, or to establish a complete formula. VpCI-377 PDS, p. 1.
Axxanol 750 can leave brownish stains, including on oil-treated cast or sintered metals touching polyethylene in hot, humid conditions. Its internal engine-oil compatibility test does not establish compatibility with every lubricant. Axxanol 750 TDS, footnotes.
Synthesis. A water barrier does not establish a water-displacement capability. A dry film does not establish paint adhesion, electrical-contact suitability, or compatibility with every elastomer and coating. Broad safety, environmental, or "free-of" language cannot establish current regulatory compliance, medical suitability, or food-contact permission for an actual part.
Protection claims and test meaning
ASTM B117-19's public scope describes a salt-fog environment, without defining product-specific specimens, exposure durations, or result interpretation. Its public significance statement warns that natural-environment performance rarely correlates with standalone salt-spray results. This is a historical edition, not a claim about the latest edition. ASTM B117-19, public scope and significance.
ASTM D1748-24 concerns relative rust prevention on steel panels under high humidity. Its public significance statement limits comparisons to similar preservative systems and applications, notes variability, and does not supply a universal exposure period or service-life prediction. Only public scope material is used here. ASTM D1748-24.
The VpCI-368 PDS reports salt-spray and humidity results but omits the tested metal grade, rust endpoint, replicate variability, and an explicit link between each result and its film condition. Its protection-period claim therefore cannot establish service life on an arbitrary part. VpCI-368 PDS, p. 1.
The LPS TDS advertises protection up to nine months outdoors and two years indoors without defining exposure severity or a corrosion endpoint. These are bounded product claims. Its specification list also carries an explicit exception to paragraph 4.6.4 of MIL-PRF-16173E Grade 2 Class 1. LPS 3 TDS, p. 1.
Synthesis. Accelerated-test hours cannot be converted into outdoor years. Packaging, surface condition, alloy, film continuity, contamination, and exposure remain part-specific. A named test or standard does not prove approval of a customer's process or a corrosion-free guarantee.
Source versions and unresolved differences
Reviewed October 30, 2026, PDT. The English VpCI-377/377 Winterized PDS is revised July 23, 2018. 377 PDS.
The English VpCI-368 PDS states last reviewed January 6, 2026. 368 PDS.
Axxanol 750 is English Rev A, copyright 2013 to 2025, without a revision date. 750 TDS.
The English LPS TDS is undated. LPS TDS. Current bulk properties here use US English SDS version 9.27, April 4, 2025. LPS SDS.
An older still-accessible US LPS 3 Bulk SDS, version 08, revised November 1, 2019, reports viscosity 20 to 550 cP without temperature, specific gravity 0.81 at 20°C, and VOC 75.58% under US state and federal consumer-product regulations. Those values have different units or disclosure bases from the 2025 sheet. Their disagreement is preserved; no reformulation or equivalence is established. Historical LPS 3 Bulk SDS, sections 9 and 16.
This coverage does not establish full ingredient composition, active-inhibitor content, lot conformity, current regional regulatory status, or performance on a particular assembly. It supplies no formulation, bath-control method, application setting, or removal procedure.
Related reference
Surface-finishing processes places temporary preservation beside broader surface-treatment operations.