Aircraft maintenance operations specify Organic Stripper for removal of multi-layer epoxy-polyurethane paint systems from 2024-T3 aluminium fuselage skins, chromated or chromate-free primed substrates, and carbon fibre reinforced plastic fairings. Brush-grade material at 25 °C is thickened to 2,500–5,000 mPa·s with 3.0–5.0 wt% cellulosic thickener measured by Brookfield RVT spindle 6 at 20 rpm. Spray-grade material is cut with 10–15 wt% dibasic ester to 80–150 mPa·s for airless spray through an orifice of 0.015–0.021 in. Dwell time for a 3-coat exterior system at 18–25 °C is 45–120 min. At skin temperatures below 10 °C, dwell time extends to 4–6 h. The stripper film must remain visibly wet throughout the dwell period. Reapplication of 0.5–1.0 L/m² is required when ambient relative humidity exceeds 70% because evaporative cooling reduces solvent activity and slows diffusion through crosslinked polyurethane topcoats.

Stripping completeness is evaluated against ASTM D6189-19. The substrate is rinsed with water at 150–200 psi through a 40° fan tip until a water-break-free surface is obtained. Adhesion of subsequent chromate-free epoxy primer is tested by ASTM D3359-17 tape pull with a minimum 5B classification. Aluminium pitting resistance is screened by 24 h immersion of bare 2024-T3 coupons followed by 10X magnification inspection. High-strength steel landing gear components are tested for hydrogen embrittlement by ASTM F519-17. The product must not contain phenol, methylene chloride, or formaldehyde when processed inside cabin metal parts. Rinse water pH is held between 6.0 and 9.0. Waste paint sludge is classified and handled under the facility NESHAP permit for paint stripping operations. Solid paint waste is not incinerated on site unless the permit specifically allows organic solvent-laden solids.

Thin-skin aluminium honeycomb bonded assemblies require an engineering concession when solvent residence exceeds 6 h because edge voids can entrain stripper and create later corrosion cells. CFRP honeycomb core configurations exhibit variable solvent uptake. Published data for this specific configuration is limited. Repair-station trials are performed on representative scarfed coupons before production use. For composite fairings, the product is not applied above 35 °C surface temperature because rapid solvent evaporation forms a dried skin that traps partially dissolved primer against the substrate. The terminal cleaned surface is re-abraded with a non-metallic abrasive pad to restore the validated surface profile before priming.

When Does Organic Stripper Replace Abrasive Blasting in Automotive Paint Shop Rework?

Mechanical abrasion of 0.7–0.8 mm electrogalvanized steel closures can generate local surface temperatures above 120 °C and distort panel curvature. Organic Stripper is specified when the substrate is high-strength low-alloy steel, 5182 or 6016 aluminium outer panels, or SMC body panels where media embedding creates adhesion defects. In immersion tanks, neat material at 25–35 °C removes acrylic-melamine clearcoat in 20–40 min. Epoxy primer removal extends to 4–6 h for fully cured layers. Racking density must not exceed 80 kg/m² of bath surface area to maintain solvent concentration. Submerged impeller agitation at 0.5–1.0 m/s prevents gel film formation at the liquid surface. Bath loading ratio is maintained at 10:1 liquid volume to dry paint solids, measured by ASTM D2369. SMC swelling after 24 h contact must be below 0.5% by the procedure of ISO 2812-1:2017. Thermoplastic polyolefin bumper covers, ABS, and polycarbonate glazing are excluded because solvent uptake exceeds 5 wt% and causes stress crazing.

After stripping, panels are rinsed with 60–80 °C alkaline power wash at 300–500 psi followed by deionized water to remove saponified binder residues. Phosphate conversion coating is re-applied before e-coat repair. Corrosion resistance of repaired e-coat is confirmed by ASTM B117-19 for 500 h with scribe creep ≤ 2.0 mm. Crosshatch adhesion of the repaired coating stack is checked by ISO 2409 with a minimum class 1. For aluminium closure panels, the stripper is used with volatile corrosion inhibitor addition at 0.2–0.5 wt% to prevent white rust during transfer. Carbon fibre reinforced thermoplastic automotive closures require short-term compatibility coupons before immersion service. The raw material is not used on magnesium alloy seat frames unless a chromate-based post-rinse is already approved because organic acid residues increase galvanic corrosion risk.

Copper(I) oxide-based self-polishing antifouling paints and epoxy anticorrosive primers on steel hull plates are removed with a thixotropic Organic Stripper gel applied at 2.0–3.0 L/m² over dry coating thicknesses of 300–800 µm. A yield stress above 60 Pa at 25 °C is required to maintain a continuous film on vertical topsides. The treated area is covered with 100 µm polyethylene sheeting for 6–12 h to reduce evaporation. Rework is needed when ambient wind speed exceeds 5 m/s because early gel skinning stops vertical diffusion. The loosened coating is scraped into sealed containers. Washdown water is not discharged directly under MARPOL Annex V and IMO Anti-Fouling Systems Convention control measures. The stripped substrate is inspected by ISO 8501-1 to achieve Sa 2½ or Sa 3 depending on the new coating specification. Salt contamination is checked by ISO 8502-6 with a limit of 20 mg/m² chloride. Solvent retention in pits must be below 20 mg/m² before re-coating; this is confirmed by gas chromatography headspace on a representative swab. The product is not used on zinc-rich epoxy primers older than 10 years where zinc corrosion products may create alkaline residues that consume the acid activator. Silyl acrylate antifouling systems require field trials because stripping activity is formulation-dependent.

Concrete Floor Coating Dissolution Windows and Moisture Vapour Transmission Limits

Removal of 100% solids epoxy, epoxy novolac, and aliphatic polyurethane floor coatings from concrete uses Organic Stripper at 0.5–1.0 kg/m² for coating thicknesses of 2–5 mm. Dwell time at 15–25 °C is 4–8 h for epoxy and 6–12 h for aliphatic polyurethane topcoats. Mechanical agitation with a 175 rpm rotary floor scrubber fitted with nylon brushes removes swollen coating from surface pores. Residual stripper is wet-vacuumed and the floor is washed with a pH-neutral detergent. On vertical concrete surfaces, the product is thickened to 10,000–15,000 mPa·s and applied in two passes. Coverage on broom-finished concrete is 0.8–1.2 kg/m²; on power-trowelled slabs, coverage decreases to 0.5–0.7 kg/m² because surface porosity is lower.

Before new coating application, the slab is tested for moisture vapour transmission rate by ASTM F1869 with a limit of 3.0 lb/1,000 ft²/24 h or by ASTM F2170 with a limit of 75% internal relative humidity. Surface pH is measured after neutralization by ASTM D4262 and must be between 7.0 and 10.0. Acid residues are neutralized with a 2–5 wt% sodium bicarbonate solution until effervescence ceases. The product is not used on asphalt mastic, bituminous substrates, or magnesium oxychloride flooring because solvent softening reduces compressive strength beyond acceptable limits. Silicone-based penetrating sealers are not dissolved; mechanical profiling remains required. Dried stripper residues in expansion joints must be removed with a soft copper brush, not steel, to avoid sparking.

FR-4 printed circuit boards carrying acrylic, urethane, or silicone conformal coatings are stripped with low-viscosity Organic Stripper at 25–40 °C in an ultrasonic bath operating at 40 kHz. Immersion time for 25–75 µm acrylic coating is 5–15 min. Urethane coatings require 30–45 min and may need a second bath when thickness exceeds 100 µm. Ultrasonic power density is held between 0.25–0.50 W/cm² to avoid delaminating glass-to-resin interfaces on FR-4 with glass transition temperature below 130 °C. Selective application for spot rework is done with polypropylene swabs, not cotton, because cellulosic fibres retain moisture and promote ionic contamination.

Process validation follows IPC-7711/7721 rework procedures. Ionic cleanliness is measured by IPC-TM-650 2.3.25 with a pass limit of 1.56 µg/cm² sodium chloride equivalent. Circuit boards with tin-lead or lead-free HASL finishes, nickel-palladium-gold pads, and glass-transition temperature above 130 °C are suitable. The product must not be used on unsealed polystyrene capacitors, unsealed switches, uncoated polycarbonate labels, or silver migration-sensitive circuits without encapsulation, because solvent uptake creates stress crazing and increases surface leakage current. Epoxy-potted assemblies are not fully stripped; published data for complete removal of anhydride-cured epoxy potting is limited. After stripping, boards are rinsed in two-stage deionized water and dried at 60 °C for 2 h before conformal coating reapplication.

If Cured Epoxy Adhesive Residues on Steel Jigs Are To Be Removed Without Surface Pitting

Steel and stainless steel jigs, meter-mix heads, and extrusion dies accumulate crosslinked two-component epoxy and polyurethane adhesive. Hot immersion in Organic Stripper at 60–80 °C for 4–8 h softens cured adhesive to a removable gel. The bath is fitted with a condenser to return solvent vapour and maintain flash-point compliance. Immersion baskets made of 316L stainless steel or Hastelloy C-276 are preferred; carbon steel baskets are not recommended because they consume acid activator and shorten bath life. Bath agitation at 1.0–2.0 m/s prevents sediment deposition on heating coils. Removal of softened adhesive uses a water jet at 1.0–2.0 bar, followed by a final wipe with isopropanol for silicone-containing residues.

Bath life is monitored by solids content using ASTM D2369 and by kinematic viscosity at 25 °C. When solids exceed 18 wt% or viscosity exceeds 1,500 mPa·s, the bath is strained and replenished at 20% v/v fresh material. Pitting resistance of 17-4 PH stainless steel jigs is checked by 24 h immersion followed by metallographic inspection at 100X. The product is not used on magnesium jigs because acid activators cause severe galvanic corrosion. Titanium jigs are acceptable for short cycles up to 8 h, but extended exposure beyond 24 h is not recommended due to possible hydride formation. Adhesive residues containing aluminium powder are not processed in the same bath because metal salts catalyze decomposition of the solvent system. Silicone rubber mandrels are not immersed; the product swells silicone beyond 15% linear dimension.

Removal of nitrocellulose lacquers, precatalyzed lacquers, and acid-catalyzed alkyd conversion varnishes from hardwood and veneer surfaces uses Organic Stripper at 1.0–1.5 L/m² applied by brush or low-pressure spray. Dwell time at 20 °C is 5–15 min for nitrocellulose and 20–40 min for conversion varnish. The stripped coating is removed with a plastic scraper in the direction of the wood grain. Neutralization of acid activator is done with mineral spirits or a 5% triethanolamine solution depending on subsequent finish chemistry. Water rinse is kept below 50 mL/m² to prevent grain raising on old growth hardwoods. Hide glue veneer bondlines are tested by applying a 2.0 MPa shear load after stripping; delamination is not acceptable. Residual solvent is flashed off for 24 h at 20–25 °C and 40–50% relative humidity before sanding sealer application. Final adhesion of the new lacquer is tested by ASTM D3359-17 with 4B or better required on production pieces. The product is not suitable for shellac-only finishes on water-sensitive substrates because water rinse raises grain beyond accepted finishing tolerance. High-solids nitrocellulose piano lacquer systems require spray booth trials because the removal window is narrower.