Corrosion Inhibitor for Petroleum & Synthetic Lubricants – 55 Gallon Drum (Cortec® M-531)

Description

Cortec® M-531 is a corrosion inhibitor package for petroleum and synthetic lubricants with strong demulsibility and outstanding non-staining properties, which is what makes it safe on coiled steel and stacked parts as well as inside turbines and gearboxes. Add it at 3 to 5 % to the base stock, or fog it into larger void spaces at 1 fl oz per cubic foot. The 55-gallon drum treats about 1,100 gallons of oil at 5 %, the scale of a turbine lube reservoir or a plant-wide gearbox program.

M-531 is Cortec’s lay-up additive for steam turbine, generator and gearbox lube systems. Cortec’s plant mothballing procedure adds it to the lubricating oil at 5 % by weight and circulates for four hours, after which the system can be left filled (wet lay-up) or drained (dry lay-up); where the oil has already been drained, M-531 is fogged into the sump, bearing housings and piping at 1 oz/ft³. It protects carbon steel, stainless steel, copper, brass and aluminum, sheds water rather than emulsifying it, and leaves no stain on finished surfaces. In oil and gas it is the lubricant additive and rust preventative for gearboxes, and turbine OEMs use it to protect the oil system as a unit comes off the test stand.

Typical applications

• Petroleum and synthetic lubricants
• Industrial lubricants needing rust and water resistance
• Coiled steel and stacked parts
• Hydraulic preservation and intermittent use
• Fogging of large void spaces
• Steam turbine and generator lube systems in wet or dry lay-up
• Gearboxes at plants preparing for seasonal or indefinite shutdown
• Turbine, pump and compressor oil systems protected as the unit leaves the test stand
• Large hydraulic pump motors idle for months
• Gearbox lubricant additive on oil and gas production equipment

How to apply M-531

1. Check compatibility. Cortec’s oil compatibility chart lists M-531 at 2 to 15 % in a long list of turbine, gear, hydraulic, compressor and engine oils, and as not compatible with several polyglycol and specific synthetic gear oils. Blend a sample of your oil first if it is not on the chart; Cortec Laboratories will test it.
2. Dose. Add 3 to 5 % M-531 to the base stock. Cortec’s turbine and generator lay-up procedure uses 5 % by weight; the Clean-Protect-Preserve field procedure uses 10 % by volume in pumps and motors. Circulate for four hours so the additive reaches bearings, coolers and piping.
3. Wet or dry lay-up. Leave the treated oil in place, or drain it. The system stays protected either way.
4. Fogging. For systems already drained, let them cool, seal all but two openings and fog M-531 into the sump, bearing housings and piping at 1 fl oz per cubic foot (1 liter per cubic meter) of void until mist reaches the exhaust port; cap it, complete the dose and seal the inlet.
5. Coiled steel and stacked parts. Add M-531 to the mill oil or preservation oil at 3 to 5 %; the non-staining film will not mark the surface where coils and sheets touch.
6. Monitor and return to service. No removal or flush is needed. Routine oil analysis (acid number, viscosity, water, dissolved metals) can continue during lay-up.
7. Storage. Store below 115 °F (46 °C); shelf life 24 months sealed.

Compatibility

Cortec’s oil compatibility chart lists M-531 as compatible at 10 % in most Mobil DTE 10 Excel, Mobilgear 600 XP, Shell Turbo and Shell Spirax grades tested, at 5 to 15 % in various Mobil SHC grades (two SHC gear oils are listed as not compatible), at 2 % in several hydraulic and gear oils, and as not compatible with polyglycol gear oils and a few specific synthetics. On elastomers it is compatible at 10 % with nitrile, Viton and PTFE. Test any oil not on the chart before dosing. See the full oil and elastomer compatibility charts.

Where it fits in the Cortec line

M-531 is the turbine and gearbox oil additive. M-535 is the ashless alternative for turbine, gear and compressor oils that must stay ash-free, and M-529 is the engine-oil package for intermittent service. VpCI-322 and VpCI-329 are the vapor-phase oil concentrates for equipment that will be drained and stored. In a full plant lay-up M-531 in the oil systems is paired with VpCI-337 fogged into voids and MilCorr shrink film outdoors. Browse the full Cortec VpCI line.

Field notes

A Virginia gantry-crane gearbox rusty inside was restored without disassembly: filled with VpCI-422, soaked 20 minutes and rotated 5 minutes, three times; drained and filled with 1:1 VpCI-414 and water, rotated 30 minutes and drained; a borescope confirmed the rust was gone; then filled with oil plus M-531 and run 5 minutes at low speed. Two years of preservation. (Cortec Case History #828)

A mobile preservation team working offshore-equipment repair shops between Houston and New Orleans adds M-531 to the oil of every rebuilt gearbox, fogs larger voids with EcoAir VpCI-337 and coats fasteners with CorShield VpCI-369 before shrink-wrapping; about 60 visits and 70 to 80 parts by mid-2024. (Cortec Case History #837)

A state-owned deepwater drilling contractor in Vietnam cold-stacked a rig with a full treatment schedule: VpCI-326 and VpCI-329 at 20% and M-531 at 5% in gearboxes, mud pumps and engines; VpCI-705 at 100 ppm in fuel; VpCI-649 BD at 0.5% in fresh-water systems; and VpCI-308 and VpCI-609 fogged into empty tanks and pipelines. (Cortec Case History #575)

Specifications

Dosage	Typically 3% to 5% in the base stock
Lay-up procedure	5 % by weight, circulate four hours; leave filled or drain
Fogging rate	1 fl. oz./cu. ft. (1 L/m³) for larger void spaces
Metals	Carbon steel, stainless steel, copper, brass and aluminum
Properties	Excellent demulsibility; non-staining, suited to coiled steel or stacked parts
Flash point (ASTM D92)	282 °F (139 °C)
Viscosity	148 cSt at 40 °C; 12.9 cSt at 100 °C
Tests	ASTM D665 turbine oil rust test methods A and B: pass; ASTM D130 copper corrosion: 1A
Base stocks	Petroleum and synthetic lubricants
Elastomers	Compatible at 10 % with nitrile, Viton and PTFE
Removal	Not required; equipment returns to service with M-531 in the oil
Storage	Below 115°F (46°C); 24-month shelf life sealed
Size	55 Gallon Drum
Shipping weight	459 lb (208 kg)
Availability	In stock
Cortec product number	12100023

Solvent Recycling Systems is an authorized Cortec® distributor. See the full Cortec VpCI line, browse the VpCI product selection guide, or contact us for volume pricing and lead times.