AD-303 Corrosion Inhibitor for Petrochemicals at Port Qasim
Phosphate-zinc-molybdate corrosion programme for petrochemical and fertiliser cooling loops at Port Qasim. Designed for sea-influenced makeup and mixed metallurgy.
Port Qasim hosts the densest petrochemical-and-fertiliser load on the Pakistan coast: Engro Polymer & Chemicals (PVC, caustic, EDC), Engro Fertilizers Daharki gas-fed urea (with Port Qasim logistics), Lotte Chemical PTA, Fatima Fertilizer's coastal terminal, the LNG regas terminal, plus the Port Qasim coal power complex sharing the same makeup water table.
Sea-influenced makeup is the structural challenge: chloride 200–600 ppm, sulphate 150–400 ppm, total dissolved solids climbing through the dry season. Carbon steel general corrosion rates without inhibition run 20–40 mpy, which is half-life on a header in under five years.
Mixed metallurgy is the second wrinkle: cooling towers at PVC and PTA plants run carbon steel headers + copper-alloy heat exchangers + galvanized fill. Protecting all three from a single programme means a phosphate/zinc/molybdate/azole blend, not a single-component inhibitor.
We're 35 km from Port Qasim. Same-day truck dispatch for emergency dosing top-ups; quarterly programme reviews bundled into the supply contract; engineer on the line for unusual events (chloride spike from intake, pH excursion from upstream chemistry change).
AD-303 is a synergistic multi-metal corrosion inhibitor: phosphate + zinc + molybdate + azole blend, active content 25–35%, pH 6.0–8.0, pale yellow liquid. Phosphate-zinc gives cathodic protection on carbon steel; molybdate + azole protect yellow metals (copper, brass). Effective across pH 7.0–9.0 with moderate hardness waters.
- Stage: dosed continuously into the cooling-tower basin or recirculating header. Maintained at a target molybdate residual of 5–10 ppm as MoO₄²⁻; that's the operational handle.
- Function: lays down a passive film on carbon steel via the phosphate-zinc cathodic mechanism. Azole + molybdate plate a separate protective layer on copper and brass surfaces. Together they suppress general corrosion to under 3 mpy on carbon steel and under 0.5 mpy on copper.
- Dose range: 80–200 ppm (as product) on the recirculating water, calibrated to molybdate residual.
- Pairing: AD-303 is dosed alongside AD-401 / AD-402 biocide rotation. Programme balance; biocide rotation on the microbial side, phosphate-zinc-molybdate on the corrosion side; is what keeps cycles-of-concentration above 5.
Where AD-303 chemistry has run on petrochemicals sites near Port Qasim.
Selected, anonymised. Site-specific case studies and references shared on supplier-qualification request.
PVC plant cooling tower · Port Qasim · 2024
AD-303 + AD-401 programme on a 18,000 m³/h tower. Carbon steel coupon corrosion 1.8 mpy across 12 months; molybdate residual held in the 6–8 ppm band.
PTA captive cooling · 2023
Replaced an imported phosphonate-zinc programme with AD-303 at 22% lower cost-in-use; corrosion rates equivalent or better on the coupon racks.
Fertiliser plant cooling · coastal terminal · 2022
AD-303 programme on a 12,000 m³/h tower with mixed-metallurgy exchangers. Cycles-of-concentration stable at 5.5 across 18 months; no exchanger pull required for cleaning.
Tell us your site, the loop, the symptom, the volume.
Same-business-day reply from Karachi with a programme outline and the relevant CoAs / SDS attached. Or WhatsApp the engineering line directly; same engineer who writes the dosing programme answers the message.