Oil Removing Agent RH-NB-1107

Alkaline Spray Degreasing of Hot-Rolled Steel Strip Prior to Continuous Galvanizing

Hot-rolled strip delivered to a continuous galvanizing line carries a mixed soil of rust-preventive mineral oil, iron fines and rolling-mill lubricant residues. In the entry cleaning section, RH-NB-1107 is combined with caustic soda and builder salts in a single-stage or two-stage spray tunnel operating at 55–75 °C. The working bath is typically maintained at 10–30 g/L of RH-NB-1107 active cleaning agent and 20–40 g/L of NaOH, with a sodium gluconate or ethylenediaminetetraacetic acid-type chelating agent at 2–5 g/L to reduce calcium and magnesium interference from hard water. Spray impingement is delivered through flooding nozzles and slit headers at 1.5–4.0 bar, creating mechanical shear that lowers the concentration required for oil displacement. Foam generation under these dynamic conditions is evaluated by the ASTM D1173-07(2014) foam-height method at 60 °C and 0.5% active-matter concentration; excessive foam collapses into oil-rich break-out tanks and disturbs downstream rinse. Cleaning effectiveness is assessed by water-break-free surface after final rinse according to ASTM F22-13, and residual oil is measured by solvent extraction of the strip surface followed by gravimetric determination. Coupon-level cleaning trials adapted from ASTM G122-20 permit the minimum effective concentration to be identified before changing line speed. Published industrial run data for lines exceeding 180 m/min are limited because residence time in the cleaning section falls below 20 s; retrofit lines often require a second brush-roll section or extended immersion tank. The product should not be combined with cationic flocculants in the same oil-separation stage because charge neutralization can destabilize the emulsion and deposit oily scum on tank walls and pipe headers.

In knit and woven cotton/polyester preparation ranges, removal of spin finish, coning oil, and knitting wax must precede bleaching and reactive dyeing to prevent hydrophobic spots, unlevel dye uptake, and needle-line oil marks. RH-NB-1107 is typically applied in a scouring bath containing 1–3 g/L of the product, 2–4 g/L caustic soda flakes, 3–6 g/L hydrogen peroxide as 35% solution, and a peroxide stabilizer at 0.5–1.0 g/L. The treatment is carried out in a soft-flow rope dyeing machine or open-width continuous range with a liquor-to-fabric ratio of 1:8 to 1:12, at 95–98 °C for 30–45 min. Under these conditions the nonionic emulsifier in RH-NB-1107 solubilizes mineral-oil-based spin finishes while alkali saponifies fatty esters and peroxide destroys natural cotton waxes and motes. Foam must remain low inside the jet chamber because air entrapment at high circulation speed causes rope ballooning and fabric tangling; low-foam performance is verified by ASTM D1173-07(2014) at 98 °C in the presence of 2 g/L NaOH and 5 g/L H₂O₂. After scouring, fabric hydrophilicity is measured by the drop-absorption method in AATCC TM79, with a pass criterion commonly set at ≤3 s for bleached cotton knit. Residual hydrophobic matter is checked by petroleum-ether extraction of the fabric and reported as oil content on weight of fibre. If residual oil exceeds 0.15% on fibre, the first exhaust dyeing may show dye spots or poor reproducibility in turquoise and navy shades. Field data from high-speed circular knits indicate that silicone-based needle oils are more difficult to remove than mineral oil; where silicone content is suspected, a pre-emulsification stage with RH-NB-1107 at 1 g/L and 60 °C for 15 min can reduce silicone carryover into the bleach bath. Alkaline stock solutions above 50 g/L NaOH should be checked for phase stability because electrolyte levels near solubility limits may depress the cloud point and produce separation.

What Limits Soil Redeposition in Multi-Stage Immersion Wash Lines for Machined Aluminium Components?

Control of soil redeposition, rather than initial oil emulsification, determines the practical cleanliness limit in multi-stage immersion wash lines for machined aluminium alloys. Aluminium-silicon alloys, particularly 6061-T6 and 380.0 die casting, carry water-soluble coolants, tapping fluids, aluminium fines and silicon dust that create a dense, fast-settling soil load. RH-NB-1107 is formulated into the wash stage at 5–20 g/L with sodium carbonate or tetrapotassium pyrophosphate to hold pH in the range 9.0–10.5, at 55–65 °C, with immersion times of 5–15 min. Ultrasonic transducers operating between 25 kHz and 40 kHz improve oil removal from blind-tapped holes, but they also raise oil loading in the bath and increase the risk of recontamination if the cleaner lacks anti-redeposition capacity. The cleaning limit is usually reached when oil loading exceeds 5 g/L or soluble silicon exceeds 200 mg/L; beyond that point, parts emerge with grey smut and water break after cleaning, even when initial cleanliness was adequate.

Water-break-free surface is assessed after final rinse according to ASTM F22-13, while alkaline attack is monitored by immersion tests adapted from ASTM G31-72a on 6061-T6 coupons exposed for 24 h at bath temperature. Any visible black smut after the immersion test indicates insufficient inhibition or excessive pH. Cleaning effectiveness for a given oil type is determined by coupon tests following ASTM G122-20, with cleaner concentration adjusted upward only after confirming that the rinse tank does not become the limiting stage. The use of strong caustic above pH 10.5 is incompatible with aluminium substrates because accelerated etching produces hydrogen gas and silicate scale. A plate coalescer or centrifugal separator should be installed on the wash tank to control oil loading below 5 g/L; when soluble silicon exceeds 200 mg/L, partial bath discard is required rather than further addition of RH-NB-1107. Industrial cleanliness data for die-cast alloys with high copper content are less consistent; cosmetic staining may appear even below the pH ceiling.

For sheepskin, pigskin, and heavy cattle hides, leather degreasing in wet-blue and pickle float applications requires emulsification of natural fats and re-adsorption inhibition rather than simple saponification. Some rawstock fat contents exceed 12% of wet-blue weight, measured by ISO 4048 extraction methods. In a tanning drum rotating at 8–12 rpm, RH-NB-1107 is applied at 0.5–2.0% on wet-blue weight in a float of 150–200% water at 40–50 °C. Sodium carbonate at 0.5–1.0% slightly raises the float pH to improve fatty acid soap formation, but excessive alkali can loosen chrome and increase effluent chemical oxygen demand. The low-foam profile matters because drum air space is limited; high-foam nonylphenol ethoxylate products produce a foam plug that reduces mechanical flexing and lowers degreasing efficiency. Fat removal is assessed gravimetrically after extraction according to ISO 4048, and a second degreasing run is typically required if residual fat exceeds 2.5% for sheepskin intended for nappa garment leather. In pickle applications, RH-NB-1107 is charged into the float before salt addition to avoid localized high-electrolyte gelation; compatibility with formic acid and sulfuric acid pickles should be confirmed because prolonged exposure below pH 2.0 can hydrolyse some nonionic esters. Spent degreasing floats containing emulsified fat contribute to high chemical oxygen demand and should be treated through dissolved air flotation or acid cracking before discharge.

When Metal Stampings Require Low-Residue Cleaning Before Zinc Phosphating

Because drawing oils, rust-preventive waxes, and metal soaps on stamped cold-rolled steel disturb phosphate crystal nucleation, the pre-phosphating cleaner must remove oil without leaving a surfactant film. In a heavy-duty immersion cleaner, RH-NB-1107 is blended into an alkaline formulation at 20–40 g/L total alkalinity, with 65–80 °C bath temperature and 5–10 min immersion. The cleaner may contain potassium hydroxide, sodium tripolyphosphate, and a non-silicate corrosion inhibitor; the RH-NB-1107 portion functions as the emulsifier and soil anti-redeposition agent. Residual cleaner after rinsing is detected by conductivity or total dissolved solids in the final rinse, with a common limit of < 200 µS/cm above incoming water. Phosphate coating weight and uniformity are then assessed by ISO 3892 or internal X-ray fluorescence methods. If rinsing is incomplete, the zinc phosphate layer becomes coarse and loose, leading to low paint adhesion in salt spray tests according to ISO 9227. Cleaning steps prior to electroplating steel parts should follow the sequence logic in ASTM B322-20, with an alkaline soak, anodic electroclean, and acid activation stages separated by counterflow rinses. The cleaner tank must be skimmed continuously because emulsified drawing oils accumulate and coat the parts during transfer if free-oil concentration in the bath exceeds 2 g/L. Uniform industry data for deep-drawn panels with high residual wax content are sparse; a solvent pre-wipe or hot high-pressure spray stage may still be required before immersion.

In indexed rotary basket spray washers, mixed-metal contract cleaning places a stricter ceiling on pH than single-substrate immersion tanks. A load may contain mild steel, zinc-plated fasteners, brass fittings, and aluminium die castings, each with different alkaline tolerance. RH-NB-1107 is used at 10–25 g/L in a potassium-hydroxide-based builder system, but pH is typically limited to 10.0–11.0 and temperature to 45–60 °C to prevent dezincification of brass and darkening of zinc. Spray pressure in an indexed cabinet washer with rotating basket is held at 2–5 bar, and stage time is 60–90 s per wash zone. Oil soil loading is controlled by a plate coalescer and overflow skimmer; without removal, emulsified oil accumulates and reduces cleaning kinetics. Tests adapted from ASTM G122-20 on SAE 1010 plain steel coupons contaminated with heat-aged cutting fluid are used to monitor bath life. Reliable field data become scarce when bath oil loading exceeds 8 g/L, because pump cavitation and foam can occur even with low-foam surfactants. The operational boundary is reached when the bath develops a stable grey emulsion and rinse water carries visible sheen; at that point the bath must be dumped and recharged. Brass loads require more frequent pH checks because dezincification can proceed silently at pH above 9.5 if cyanide-free brass cleaners are not buffered correctly.

Vacuum Heat Treatment of Bearing Rings Requires Solvent-Free Precleaning with Controlled Alkali Ratio

A bearing ring entering a vacuum heat-treatment furnace after grinding carries residual rust-preventive oil, lapping compound, and metallurgical coolant. Before vacuum carburizing or through-hardening, traces of hydrocarbon residues crack under low-pressure heating and produce carbon contamination on furnace heating elements and graphite fixtures. RH-NB-1107 is applied in an aqueous immersion and spray precleaning stage at 15–25 g/L with sodium hydroxide and gluconate, at 60–70 °C for 8–12 min. Final rinsing uses deionized water with conductivity below 5 µS/cm; any residual alkalinity can cause staining after tempering. Cleanliness is verified by water-break-free testing according to ASTM F22-13 and by particle extraction and gravimetric analysis according to ISO 16232-3:2018 or equivalent component cleanliness methods. For bearing rings with narrow annular grooves, spray impingement from vertical headers at 3–5 bar is more effective than air agitation alone. The cleaning bath should not be allowed to accumulate oil above 3 g/L, because emulsified oil can form a thin film inside the rings and lead to local soft spots after austenitizing. Documented production data for very high-viscosity rust-preventive compounds remain limited; such soils may require a two-stage sequence with a hot pre-soak and an ultrasonic wash before final spray rinse.