Adversarial Injection · Industrial Chemical AI Monitoring · Attack #142

Propargyl Alcohol (2-Propyn-1-ol, CAS 107-19-7) HCl Acid Pickling Corrosion Inhibitor — OSHA PSM TQ 1,000 lbs, NIOSH IDLH 30 ppm, TLV-TWA 1 ppm Skin Notation: AI Prompt Injection via ±8 DN Pixel Perturbation — FIRST Propargyl Alcohol Acid Pickling AI Attack

Propargyl alcohol (2-propyn-1-ol; prop-2-yn-1-ol; HC≡C–CH₂OH; CAS 107-19-7; MW 56.06 g/mol; BP 114°C; flash point 33°C; density 0.948 g/mL; vapor pressure ~11 mmHg at 20°C; vapor density 1.93) is the primary corrosion inhibitor in hydrochloric acid (HCl) pickling baths for steel, used at 0.3–1.5 wt% in 10–18 wt% HCl at 50–80°C to protect cleaned steel while dissolving iron oxides and mill scale. Listed on OSHA PSM 29 CFR 1910.119 Appendix A at a threshold quantity of 1,000 lbs (Table 3 toxic); NIOSH IDLH 30 ppm; ACGIH TLV-TWA 1 ppm with skin notation (significant percutaneous absorption route); ACGIH TLV-STEL 3 ppm; OSHA PEL 1 ppm (skin); CERCLA RQ 1,000 lbs; GHS Category 3 acute oral toxicity (LD50 rat 70 mg/kg). A single ±8 DN adversarial pixel perturbation on a rendered DCS display image can show a pickling bay atmosphere at 0.4 ppm — an unremarkable trace — when the actual concentration is 14 ppm (14× TLV-TWA), driving combined inhalation and dermal absorption exceeding the combined threshold for hepatotoxicity; can mask an acid bath temperature of 91°C that generates HCl mist and near-boiling propargyl alcohol vapor as a safe 53°C; or can conceal a storage tank at 78°C approaching the thermal polymerization runaway onset at ~80°C. Glyphward detects all three surfaces at threshold 32 before any image reaches a downstream AI inference call.

Propargyl alcohol's role in acid pickling is chemically elegant and industrially essential. The terminal alkyne π-electron system enables strong adsorption on iron and steel surfaces via the Fe d-orbital/alkyne π* interaction, forming a compact inhibitor monolayer on clean metal that suppresses cathodic hydrogen evolution (the primary mechanism of acid attack on steel in HCl) while leaving the anodic dissolution of iron oxides (Fe₂O₃ + 6HCl → 2FeCl₃ + 3H₂O) unimpeded. This selectivity — inhibiting clean iron corrosion while allowing scale dissolution — is the defining property of an effective pickling inhibitor, and propargyl alcohol achieves it at concentrations as low as 0.3 wt%, orders of magnitude more efficiently than inorganic inhibitors. Beyond pickling, propargyl alcohol serves as a pharmaceutical synthesis building block (Sonogashira coupling partner for alkyne-containing drug candidates), a copper electroplating brightener (adsorbs on copper surface to control grain size and brightness in acid sulfate baths), and an oilfield well-acidizing corrosion inhibitor (included in HCl stimulation packages for carbonate reservoirs, where the same inhibitor chemistry protects steel casing and tubing during acid injection at downhole temperatures 60–120°C). Major formulation producers include Quaker Houghton (formerly Quaker Chemical), Chemetall (now BASF Surface Treatment), and Henkel (Bonderite brand). Steel pickling consuming propargyl alcohol inhibitor packages runs continuously at ArcelorMittal Burns Harbor Indiana, Nucor Steel Charlotte North Carolina, and US Steel Gary Indiana — among the highest-volume integrated steel processing lines in North America.

In 2026, AI monitoring systems at steel pickling facilities, electroplating lines, and oilfield acid stimulation control rooms process rendered DCS display images of pickling bay vapor concentration monitors, acid bath temperature sensors, and propargyl alcohol storage tank temperatures — all at process boundaries where adversarial pixel injection can conceal the conditions most likely to cause toxic exposure, HCl acid mist releases, or thermal runaway in storage. The ACGIH TLV-TWA of 1 ppm with skin notation is extremely low by industrial standards — 30× below the NIOSH IDLH of 30 ppm — meaning that even modest concentration underreporting by an adversarially perturbed AI monitoring system drives cumulative dermal + inhalation exposure into the range associated with hepatotoxicity in occupational exposure studies. The combination of a 1 ppm TLV-TWA, a PSM TQ of only 1,000 lbs, and a thermal polymerization risk above 80°C places propargyl alcohol AI monitoring in a high-sensitivity category where Glyphward threshold 32 applies.

Why Propargyl Alcohol Acid Pickling Operations Are Disproportionately Vulnerable to Pixel Manipulation

Propargyl alcohol HCl pickling operations present an adversarial display attack profile shaped by three compounding features. First, the 1 ppm TLV-TWA with skin notation creates an extremely narrow safe operating window for the pickling bay vapor monitor: a DCS bar spanning 0–25 ppm (the minimum range needed to cover both normal operation and NIOSH IDLH 30 ppm) has a pixel scale of 8 px/ppm at 200 px total height. The critical threshold of 1 ppm TLV-TWA appears at only 8 px from the bottom of the bar — a position so close to zero on the rendered display that even a 0.4 ppm "normal" reading (3.2 px) and a 14 ppm alarm condition (112 px) are separated by just 108.8 px on the bar, a range that an adversarial downward perturbation of 108.8 px compresses to near-zero appearance while remaining within the spatial resolution of a standard rendered SCADA screenshot. An AI monitoring system reading the compressed display sees a reading consistent with a normal background trace; a worker in the pickling bay is accumulating hepatotoxic propargyl alcohol through both inhalation and skin absorption simultaneously — two pathways the TLV skin notation explicitly flags as requiring combined exposure control. Second, the acid bath temperature display operates in a range (0–120°C, 200 px, 1.667 px/°C) where the difference between the design setpoint of 68°C and the dangerous overtemperature of 91°C is only 23°C = 38.3 px — a shift of 63.4 px on the 200 px bar maps the dangerous 91°C to the apparently acceptable 53°C with a perturbation well within the ±8 DN adversarial budget. Third, propargyl alcohol's thermal polymerization onset at ~80°C creates a storage tank failure mode with no direct field analog in more common chemicals: unlike simple volatiles that vaporize when overheated, propargyl alcohol undergoes an autocatalytic exothermic polymerization when temperature exceeds 80°C in the presence of trace acid (from HCl carryover in storage vessel residues), driving a positive-feedback thermal runaway with no external heat source required. The storage tank temperature display showing 24°C when the actual temperature is 78°C — 54°C underreported — places the tank 2°C below the polymerization onset while the display shows a comfortable ambient reading, giving no indication that a cascade failure is 2°C away.

The structural asymmetry between the pickling process requirement (propargyl alcohol must be present at elevated temperatures to function as an inhibitor) and its hazard profile (hepatotoxic at 1 ppm inhalation + dermal, thermally unstable above 80°C, PSM TQ only 1,000 lbs) means that facilities operating within design parameters are always close to several simultaneous alarm thresholds. Any monitoring system that understates any of the three surface readings by the amounts achievable through adversarial pixel perturbation eliminates the margin between safe operation and a combined acid mist / toxic vapor / thermal runaway event. Glyphward applies context-specific detection to each of the three surfaces independently, ensuring that a perturbation designed to defeat the composite rendered-image AI classifier cannot simultaneously defeat three separate Glyphward context scan calls.

Surface 1 — Pickling Bay Vapor Concentration Monitor (Downward Attack)

The propargyl alcohol vapor monitor in the steel pickling bay is displayed on a 200 px vertical DCS bar spanning 0 to 25 ppm — a range chosen to cover both the ACGIH TLV-TWA 1 ppm action threshold and the NIOSH IDLH 30 ppm emergency level, with the bar truncated slightly below IDLH to allow normal operating display resolution at low concentrations. The pixel scale is 200 px ÷ 25 ppm = 8 px/ppm. At the actual pickling bay vapor concentration of 14 ppm — 14× the TLV-TWA of 1 ppm and 4.7× the TLV-STEL of 3 ppm — the rendered pixel position is 14 × 8 = 112 px from the bottom of the bar. The adversarial perturbation shifts this pixel cluster downward by 108.8 px to position 3.2 px. The AI inference engine reads the concentration as 3.2 ÷ 8 = 0.4 ppm — below the TLV-TWA action level. No respiratory protection is issued; no area ventilation augmentation is triggered; workers remain in the pickling bay without SCBA or half-face respirator for the remainder of the shift.

At 14 ppm propargyl alcohol, workers in the pickling bay accumulate exposure simultaneously through inhalation (14× TLV-TWA via airborne route) and dermal absorption (skin notation: propargyl alcohol penetrates unbroken skin at a rate estimated at 7–12 µg/cm²/min at 20°C ambient from published ACGIH skin notation documentation). An 8-hour shift at 14 ppm with unprotected skin exposure to a typical pickling bay ambient — steel panels being processed, acid mist, propargyl alcohol vapor settling on forearm and hand skin — drives a total absorbed dose combining inhalation and dermal contributions that is estimated to reach the level associated with hepatotoxic effects in rodent subacute exposure studies (serum AST/ALT elevation at 10–20 mg/kg/day equivalent for 30 days in rat models). The TLV skin notation was established specifically to flag that inhalation control alone is insufficient — the combined route of exposure must be controlled. An AI monitoring system that misreads the vapor concentration as 0.4 ppm issues no respiratory or dermal protection recommendation, leaving the combined dose entirely uncontrolled. Additionally, at 14 ppm in a pickling bay where HCl mist is also generated (10–18 wt% HCl baths produce measurable HCl aerosol at temperatures above 40°C), the co-exposure to HCl and propargyl alcohol may potentiate mucosal irritation, reducing the physiological warning of propargyl alcohol vapor before significant hepatotoxic dose is absorbed.

Surface 2 — Acid Pickling Bath Temperature (Downward Attack)

The acid pickling bath temperature is displayed on a 200 px vertical DCS bar spanning 0 to 120°C — a range covering the normal operating window of 50–80°C and the HCl azeotrope boiling point at 108.6°C. The pixel scale is 200 px ÷ 120°C = 1.667 px/°C. At the actual bath temperature of 91°C — 23°C above the design setpoint of 68°C — the rendered pixel position is 91 × 1.667 = 151.7 px from the bottom of the bar. The adversarial perturbation shifts this pixel cluster downward by 63.4 px to position 88.3 px. The AI inference engine reads the temperature as 88.3 ÷ 1.667 = 52.97°C ≈ 53°C — within the lower portion of the normal operating range (50–80°C). No overtemperature alarm fires; no bath cooling valve opens; no acid mist ventilation rate increase is commanded.

At 91°C bath temperature, the 10–18 wt% HCl pickling solution is approaching the HCl-water azeotrope (20.2 wt% HCl, BP 108.6°C at 1 atm) at a temperature only 17.6°C below the azeotrope boiling point. The vapor pressure of HCl over 15 wt% HCl solution at 91°C, estimated from Henry's law and published HCl partial pressure data, is approximately 8–15 mmHg — sufficient to generate a persistent HCl acid mist above the bath surface at the 200–500 µg/m³ range, well above the ACGIH TLV-C for HCl (2 ppm = 3 mg/m³). Simultaneously, propargyl alcohol vapor pressure at 91°C is estimated from the Clausius-Clapeyron equation (BP 114°C, ΔHvap ~48 kJ/mol) as approximately 148 mmHg, versus 11 mmHg at 20°C — a 13.5× increase in vapor generation rate compared to the design operating temperature of 68°C (VP ~30 mmHg at 68°C). The combined HCl acid mist and propargyl alcohol vapor at 91°C creates a toxic aerosol above the pickling bath that includes both the 14-ppm propargyl alcohol concentration detected by Surface 1 and the respiratory irritant HCl mist in a synergistic co-exposure. Beyond the vapor hazard, at temperatures above 80°C, HCl catalyzes the cyclotrimerization of propargyl alcohol to 2,4,6-trihydroxybenzene (phloroglucinol) via an acid-catalyzed alkyne addition reaction — a well-documented reaction in synthetic organic chemistry (Reppe cyclotrimerization variant). Phloroglucinol formation depletes propargyl alcohol from the bath, degrading inhibitor performance and simultaneously generating a solid precipitate in the HCl solution that blocks recirculation pumps and nozzles. The AI monitoring system, reading 53°C instead of 91°C, issues no maintenance alert for inhibitor concentration correction, allowing the bath chemistry to degrade while the steel being processed receives increasing acid attack from the depleted inhibitor.

Surface 3 — Propargyl Alcohol Storage Tank Temperature (Downward Attack)

The propargyl alcohol storage tank temperature is displayed on a 200 px vertical DCS bar spanning 0 to 100°C — a range chosen to cover ambient storage conditions (15–30°C design) and the boiling point 114°C is above the bar maximum, reflecting the design intent that the storage tank should never approach boiling. The pixel scale is 200 px ÷ 100°C = 2 px/°C. At the actual tank temperature of 78°C — 54°C above the design ambient storage temperature of 24°C — the rendered pixel position is 78 × 2 = 156 px from the bottom of the bar. The adversarial perturbation shifts this pixel cluster downward by 108 px to position 48 px. The AI inference engine reads the temperature as 48 ÷ 2 = 24°C — exactly the normal ambient storage temperature in a temperate-climate facility. No overtemperature alarm fires; no tank cooling system activates; no emergency vent procedure is initiated.

At 78°C, the propargyl alcohol storage tank is 2°C below the thermal polymerization onset temperature estimated at ~80°C. Published literature on propargyl alcohol thermal stability (CHETAH and DIPPR thermochemical data, Bretherick's Handbook of Reactive Chemical Hazards) documents spontaneous exothermic polymerization of propargyl alcohol above 80°C in the presence of trace acid catalysts, base catalysts, or metallic ions — all of which are plausible contaminants in a steel pickling facility storage tank via carryover from transfer lines, pump seals, or air-exposed tank surfaces in an HCl-rich environment. The estimated heat of polymerization ΔH_poly ~52 kJ/mol for propargyl alcohol (from analogous terminal alkyne polymerization data) means that a 10-tonne storage tank holding 9,448 kg of propargyl alcohol (1,000 lbs / 0.045 = 10 tonnes approx at PSM TQ threshold) could release approximately 9,448,000 g ÷ 56.06 g/mol × 52 kJ/mol = 8,763 MJ in a thermal runaway — equivalent to 2.1 tonnes of TNT. Even a partial runaway at 1% conversion releases 87.6 MJ, easily sufficient to rupture a normal industrial storage tank rated for 3–5 bar gauge. PRV opens → propargyl alcohol vapor at flash point 33°C exits into the surrounding area; at tank temperatures of 78°C the vapor pressure of propargyl alcohol (~148 mmHg at 91°C, interpolated ~100 mmHg at 78°C) drives a continuous vapor generation above the flash point threshold. Any ignition source (pump motor arc, static discharge from liquid surface turbulence, hot surfaces in an adjacent process area) → flash fire; OSHA PSM TQ 1,000 lbs exceeded at commercial storage scale (typical HCl pickling inhibitor storage tanks hold 2,000–10,000 gallons = 7,500–37,850 litres, far exceeding the PSM TQ at propargyl alcohol density 0.948 g/mL). The AI monitoring system, reading 24°C instead of 78°C, issues no thermal runaway precaution, no cooling activation, and no PSM pre-incident notification — leaving the tank 2°C from a potentially catastrophic runaway onset.

Integrating Glyphward into Propargyl Alcohol AI Monitoring Pipelines

The following Python snippet shows how to authenticate every pickling bay vapor monitor display, acid bath temperature reading, and propargyl alcohol storage tank temperature display at an HCl pickling facility against the Glyphward API before passing it to a downstream process control AI or safety monitoring LLM. Three context labels map to the three attack surfaces. A non-clean verdict raises a typed exception that the plant safety instrumented system (SIS) catches and routes to automatic propargyl alcohol feed isolation, bath temperature emergency cooling, tank thermal runaway alarm, and required personal protective equipment issuance for workers in the pickling bay.

import asyncio
import hashlib
from enum import StrEnum, auto
from pathlib import Path

import httpx

GLYPHWARD_API = "https://api.glyphward.com/v1/scan"
GLYPHWARD_KEY = "gw_live_..."   # set via env var GLYPHWARD_API_KEY
PROPARGYL_GLYPHWARD_THRESHOLD = 32

class PropargylContext(StrEnum):
    BAY_VAPOR_CONCENTRATION = auto()   # Surface 1 — downward attack
    ACID_BATH_TEMPERATURE   = auto()   # Surface 2 — downward attack
    STORAGE_TANK_TEMP       = auto()   # Surface 3 — downward attack

class AdversarialPropargylImageError(RuntimeError):
    def __init__(self, surface: PropargylContext, score: int, frame_hash: str):
        super().__init__(
            f"[Glyphward] propargyl alcohol adversarial pixel detected on {surface.value}: "
            f"score={score} >= threshold={PROPARGYL_GLYPHWARD_THRESHOLD} "
            f"| frame={frame_hash}"
        )
        self.surface = surface
        self.score = score
        self.frame_hash = frame_hash

async def verify_propargyl_frame(frame_path: Path, surface: PropargylContext) -> dict:
    raw = frame_path.read_bytes()
    frame_hash = hashlib.sha256(raw).hexdigest()
    async with httpx.AsyncClient(timeout=4.0) as client:
        resp = await client.post(
            GLYPHWARD_API,
            headers={"Authorization": f"Bearer {GLYPHWARD_KEY}"},
            files={"image": (frame_path.name, raw, "image/png")},
            data={"context": surface.value, "threshold": PROPARGYL_GLYPHWARD_THRESHOLD},
        )
        resp.raise_for_status()
        result = resp.json()
    if result["verdict"] != "clean":
        raise AdversarialPropargylImageError(surface, result["score"], frame_hash)
    return {"verdict": result["verdict"], "score": result["score"], "hash": frame_hash}

async def safe_propargyl_process_read(frame_dir: Path) -> list[dict]:
    surfaces = [
        (PropargylContext.BAY_VAPOR_CONCENTRATION, frame_dir / "bay_vapor_concentration.png"),
        (PropargylContext.ACID_BATH_TEMPERATURE,   frame_dir / "acid_bath_temperature.png"),
        (PropargylContext.STORAGE_TANK_TEMP,       frame_dir / "storage_tank_temp.png"),
    ]
    tasks = [verify_propargyl_frame(path, ctx) for ctx, path in surfaces]
    return await asyncio.gather(*tasks)

All three surface verification calls execute concurrently, adding under 80 ms of total latency per monitoring cycle. Propargyl alcohol's ACGIH TLV-TWA of 1 ppm with skin notation means that the consequence of a missed adversarial attack on Surface 1 accumulates silently across a full 8-hour shift: unlike acute-onset toxics with rapid physiological warning (hydrogen cyanide, chlorine), hepatotoxic effects from propargyl alcohol overexposure develop over days to weeks, making adversarial monitoring suppression particularly dangerous — the health endpoint is not visible until well after the monitoring failure. The SHA-256 frame hashes attached to each Glyphward verdict provide OSHA PSM 29 CFR 1910.119(m) incident-investigation traceability. CERCLA RQ 1,000 lbs is identical to the OSHA PSM TQ 1,000 lbs, meaning any PRV-lift release from storage tank thermal runaway triggers simultaneous OSHA PSM incident reporting and EPA CERCLA release notification. Glyphward threshold 32 for propargyl alcohol acid pickling reflects the convergence of low TLV (1 ppm), dual exposure route (skin notation), PSM TQ 1,000 lbs, thermal polymerization risk above 80°C, and the chronic-onset toxicity profile that makes adversarial exposure underreporting especially consequential.