77-2 Metal Cleaning Agent and Anti-rust Agent functions as an aqueous alkaline cleaning and interstage corrosion-inhibitor fluid for ferrous metal manufacturing. The working bath is prepared by diluting the concentrate with deionized or reverse-osmosis water having conductivity below 50 µS/cm; water hardness above 150 mg/L CaCO₃ reduces anti-rust film uniformity and produces scale on heating coils. The product is supplied as a liquid concentrate and is applied only to ferrous substrates unless specific compatibility testing on aluminium, zinc, magnesium, or copper alloys has been completed. Bath preparation, replenishment, and discharge must follow the safety data sheet and local wastewater permits. The application scope covers machined automotive components, high-strength fasteners, precision bearing elements, cold-formed transmission parts, steel packaging, and maintenance-overhaul components. The following scenarios describe process conditions, compliance anchors, addition ratios, and terminal products for specific downstream processes.

On automotive powertrain machining lines producing grey cast iron caliper bodies, 42CrMo4 steel wheel hubs, and differential bearing caps, aqueous cutting fluid residues are removed before assembly-facing surfaces are milled and before final rust-preventive oil is applied. In immersion cells, the 77-2 working bath is controlled at 6–8 vol% concentration, pH 9.2–9.7, and temperature 55–65 °C; contact time is 4–7 min. Spray-washer stages for the same part families operate at 3–5 vol%, 50–60 °C, and 1.5–2.5 bar nozzle pressure. The production sequence consists of loading baskets onto an overhead monorail, primary wash, drain zone, second spray rinse at conductivity below 25 µS/cm, air-knife blow-off at 4 bar, and dry-off at 80–90 °C for 6–10 min. Terminal products include brake calipers, wheel hubs, steering knuckles, and differential bearing caps. Compliance for exported assemblies follows IATF 16949:2016 clause 8.6.1.1 cleanliness requirements, while corrosion protection is validated under ISO 9227:2022 neutral salt spray for 24–48 h or ISO 6270-2:2022 condensation humidity at 40 °C and 100% RH for 72 h without red rust. Process limits observed on production-scale immersion lines show that concentrations above 9 vol% can leave visible white inhibitor residue in blind M8 tapped holes after dry-off, while concentrations below 4 vol% allow flash rust on machined cast iron within 2 h in unheated staging bays. Baskets containing stacked parts require incremental rotation at 3 rpm for blind-hole drainage; otherwise localized pitting is found at internal threads after field returns. The bath is skimmed with a belt oil separator and filtered through 25 µm bag filters to prevent redeposition of metal fines.

Fastener Pre-Treatment Lines and the Cleaner-to-Phosphate Transition

High-strength steel fasteners of property classes 10.9 and 12.9 for automotive chassis joints are cleaned and given interstage anti-rust protection before zinc phosphate conversion. The 77-2 bath is charged at 5–7 vol% in the first stage of a five-stage power spray tunnel at 60–70 °C; stage-one contact time is 2–3 min. Stage two rinses with mains water at 25–35 °C and conductivity below 30 µS/cm. Stages three and four apply zinc phosphate per ISO 9717:2024 and a cold water rinse; stage five applies a chromate-free passivation. Terminal products include M10–M20 hex flange bolts, wheel bolts, stabilizer link studs, and steering rack bolts. Compliance anchors include ISO 898-1:2013 for mechanical properties, ISO 9227:2022 for phosphate-plus-seal salt spray resistance over 72 h, and REACH Regulation (EC) No 1907/2006 Annex XVII for restricted substances in EU export. A process conflict occurs at the cleaner-to-phosphate transition: drag-out from stage one raises free acid in the phosphate bath when carry-over exceeds 0.3 L/100 kg of fasteners, shifting coating weight and crystal morphology. Operators titrate the cleaner bath at 12–18 mL total alkalinity and 6–9 mL free alkalinity; if free alkalinity drifts below 5 mL, rinse corrosion appears on washer internal surfaces. The anti-rust component permits 4–6 h transfer time from stage two to phosphate without red rust. Foam generation above 2.5 bar spray pressure at 7 vol% requires defoamer addition, which shortens oil-skimmer interval. Published data for the exact foam collapse rate under this specific phosphate-line configuration is limited; lot release is therefore controlled by a bench-top spray cell test using a 10 mL/L sample.

Residual film interference on rolling bearing vibration signatures has been investigated on DIN 625-1 deep-groove ball bearing rings and linear guide rails before preservative oil application. The 77-2 fluid is used in ultrasonic immersion cells at 4–6 vol%, pH 9.0–9.5, and 45–55 °C for 3–5 min, followed by two counterflow rinses with deionized water at 40 °C. Cleaning performance is verified by particle count according to ISO 16232:2018; the acceptance limit for high-precision bearing rings is ≤100 particles ≥5 µm per component. The anti-rust effect is validated under ISO 6270-2:2022 condensation conditions for 48 h. Terminal products include 62-series electric motor bearings, bicycle hub bearings, spindle bearing races, and linear motion blocks. A critical threshold arises when the working concentration exceeds 7 vol%: residual inhibitor film thickness on raceways increases roughness by 0.02–0.05 µm Ra, and vibration velocity measured under ISO 15242-1:2015 elevates by 10–25 µm/s in the medium-frequency band from 50–300 Hz on finished assembled bearings. Below 3 vol%, flash rust on ground raceways appears within 30 min at relative humidity above 60%. Shielded or sealed bearing rings must be tilted 15° during ultrasonic treatment to release trapped air; otherwise the anti-rust film is absent behind the shield. Rinse tank conductivity is maintained below 20 µS/cm because residual salts contribute to electrical impedance changes in motor bearings. The production constraint is not solubility but film uniformity on superfinished surfaces; load density above 15 kg per 20 L ultrasonic bath leads to non-uniform film and requires reduction to 10 kg/20 L.

When Cold Forming Lubricants Must Be Removed Before Quench Hardening

Transmission synchronizer sleeves, gearshift forks, and CV joint inner races formed with chlorinated or phosphate-ester lubricants are processed through a rotary drum washer before controlled atmosphere quench hardening. In this configuration the 77-2 bath is charged at 6–10 vol% at 65–75 °C, pH 9.2–10.0, with cycle time 8–12 min in a continuous rotary drum and countercurrent rinse. Rinsing uses tempered water below 25 µS/cm and is followed by 90 °C hot air drying for 8–12 min. Terminal products include synchronizer hubs, gearshift forks, CV joint inner races, and bearing cages. Compliance is linked to CQI-9 heat treatment system assessment and AMS 2750F pyrometry; surface chloride before heat treatment is checked by ISO 8502-2:2005 with acceptance limit <10 mg/m² to avoid stress corrosion and furnace liner attack. The main process conflict is thermal: the anti-rust film breaks down at approximately 110 °C, but undried pockets at blind bores carry cleaner residue into the quench furnace, where carbonate residues reduce furnace atmosphere carbon potential and produce non-uniform case depth. Bath concentration is therefore held in the lower half of the range, 6–7 vol%, for parts with blind holes, accepting a shorter humidity protection interval. At 10 vol%, drain time must be extended by 2 min to avoid residue bridging. Data from production-scale rotary washers indicate that bath life declines when tramp oil exceeds 5% by volume as measured by refractometer; the cleaning rate for chlorinated forming oil drops by half and leads to localized soft spots in gear teeth after carburizing. The recommended oil skimming and centrifuge loop is 0.5–1.0 bath turnover/h. This fluid is not suitable for aluminium synchronizer rings above 45 °C due to alkaline etching.

Steel Pail and Aerosol Can Sidewall Washing Before Exterior Lacquer

Steel aerosol can bodies and 20-L pail sidewalls coming from tandem welding and necking lines are cleaned and given temporary rust protection before exterior base coating or powder coating. The 77-2 bath is sprayed at 2–4 vol% and 40–50 °C; contact time is limited to 20–40 s in a high-speed in-line washer with 1.0–1.5 bar fan nozzles. The process sequence includes pre-rinse, cleaner stage, municipal water rinse at 20–30 °C, forced ambient air blow-off, and dryer zone at 70–80 °C. Terminal product types are decorated aerosol containers for automotive paints and lacquers, steel pails for solvent-based adhesives and sealants, and tinplate drum closures. Compliance references include UN 1A2 package certification for steel pails and closures, REACH Regulation (EC) No 1907/2006 for chemical restrictions, and RoHS Directive 2011/65/EU for exported packaging components where applicable. A lower concentration is required because can sidewall coverage at high line speeds would otherwise leave inhibitor streaks that interfere with lacquer adhesion; a cross-cut tape adhesion test per ISO 2409:2013 is used after coating, and values fall from Gt 0 to Gt 2 when cleaner concentration exceeds 5 vol%. Foam generation in the high-shear nozzle system is controlled by liquid level rather than defoamer; the bath tank is fitted with a low-level float switch at 150 mm from pump suction. Bath temperature above 60 °C accelerates corrosion protection but causes lacquer blistering on unrinsed seams. The anti-rust component provides 24–48 h indoor storage protection at 20–25 °C and 50% RH when verified by ISO 6270-2:2022, sufficient between washing and coating shifts.

Maintenance overhaul of API 610 centrifugal pump casings and gear reducer housings uses the compound as a cold cleaner and flash-rust inhibitor during teardown and reassembly. In open parts washers, concentration is 5–10 vol% at 40–55 °C; for manual brushing, the same dilution is applied with an acid brush, allowed 5–10 min dwell, then rinsed with water below 30 µS/cm. The process begins with removal of old grease by scraping, followed by circulation through a 100 L stainless steel parts washer with 50 µm strainer, rinse, compressed air blow-down at 3 bar, and application of a heavier preservative oil for long-term storage. Terminal products include overhauled centrifugal pumps, gear reducers, fan shaft assemblies, and valve bodies. Compliance for industrial maintenance uses ISO 12944-2:2017 corrosivity category C2 indoor protection; surface salts are measured by ISO 8502-2:2005 and limited to <10 mg/m² for painted assemblies. Operational boundaries include avoiding copper alloy shafts and bronze impellers at concentration above 7 vol% and temperature above 55 °C; brass and copper components can tarnish. Cast iron housings with absorbed oil require replenishment at 1.5–2.0 vol% per 8 h shift because the cleaner emulsifies tramp oil and reduces active alkalinity. The anti-rust film is intentionally thin and provides 24 h indoor protection; extended storage beyond 48 h without preservative oil application is outside the validated operating window. Published data for humidity resistance on machined cast iron in unheated tropical sheds is limited; field verification at 35 °C and 85% RH is recommended before relying on the compound as a sole preservative.