Formulation Guides

Raw Material Checklist for Anti-Corrosive Zinc-Rich Primer

Zinc-rich primers are the first line of defence against corrosion on structural steel, offshore platforms, pipelines, and industrial equipment across the GCC. In Saudi Arabia, Qatar, and the UAE, where humidity, salt spray, and extreme temperatures accelerate corrosion, a well-formulated zinc-rich primer can be the difference between a 5-year and a 25-year asset life. This guide covers the complete raw material checklist for formulating both organic (epoxy-based) and inorganic (silicate-based) zinc-rich primers.

Understanding Zinc-Rich Primer Types

There are two main categories, each with distinct raw material requirements:

• Organic Zinc-Rich Primers — use epoxy, polyurethane, or chlorinated rubber as the binder. More flexible, easier to apply, and more forgiving of surface preparation variations.
• Inorganic Zinc-Rich Primers — use ethyl silicate or water-based silicate as the binder. Harder, more temperature-resistant, and typically required for high-performance industrial specifications. Used widely in Saudi Arabia for structural steel on giga-projects.

Complete Raw Material List — Organic Epoxy Zinc-Rich Primer

Raw Material	Function	Typical % (wet weight)	Notes
Zinc Dust (Grade 1, D50 ~5μm)	Sacrificial anodic protection	60–70%	Must comply with ASTM D520 Type II or ISO 3549
Liquid Epoxy Resin (BPA, EEW 182–192)	Film-forming binder (Part A)	8–12%	Bisphenol A epoxy, CAS 25068-38-6
Reactive Diluent (benzyl alcohol / BGE)	Viscosity reduction	2–4%	Reduces viscosity without raising VOC excessively
Polyamide or Phenalkamine Hardener	Crosslinker (Part B)	8–12%	Mix ratio must be precise; phenalkamine for humid GCC conditions
Micronised Talc (platey grade)	Anti-settling, barrier reinforcement	3–5%	Platey morphology reduces zinc settlement in storage
Silica / Treated Fumed Silica	Anti-sag, rheology control	0.5–1.5%	Critical for preventing sag on vertical surfaces
Anti-settling Agent (e.g. organobentonite)	Prevents zinc dust settlement	0.3–0.8%	Soft settling only — hard settling (caking) must be avoided
Xylene / Aromatic 100 Solvent	Viscosity, flow, application	5–10%	Check VOC limits per SASO or project specification
Adhesion Promoter (silane-based)	Steel substrate adhesion	0.2–0.5%	Improves adhesion especially in humid conditions
Wetting & Dispersing Agent	Zinc dust dispersion in Part A	0.3–0.6%	Prevents zinc agglomeration during storage

Raw Material List — Inorganic Ethyl Silicate Zinc-Rich Primer

Raw Material	Function	Typical %	Notes
Zinc Dust (Grade 1, D50 ~4μm)	Sacrificial protection	75–85%	Higher loading than organic type
Tetraethyl Orthosilicate (TEOS) / Pre-hydrolysed Ethyl Silicate	Inorganic binder	10–15%	Must be pre-hydrolysed; water or acid-catalysed
Isopropyl Alcohol (IPA)	Solvent / hydrolysis medium	5–10%	CAS 67-63-0; also acts as viscosity reducer
n-Butanol	Co-solvent, slow evaporator	2–5%	Improves film coalescence and reduces mud cracking
Fumed Silica (hydrophilic)	Anti-settling, thickening	0.5–1.0%	Must be well-dispersed to avoid gelling
Hydrochloric or Phosphoric Acid (catalyst)	Hydrolysis catalyst	0.05–0.1%	Trace amount only; pH must be controlled

Critical Formulation Parameters

Getting these parameters right is as important as the raw material selection itself:

• Zinc content in dry film: Minimum 65% by weight for organic, 80% for inorganic (per SSPC Paint 20 Level 2). Saudi Aramco specs often require testing to confirm this after application.
• Surface preparation: Sa 2.5 (ISO 8501-1) minimum — near-white blast. In GCC industrial projects, Sa 3 is commonly specified. The zinc primer cannot compensate for poor surface preparation.
• Pot life: Organic epoxy zinc-rich primers typically have 4–8 hours pot life at 25°C. In Saudi summer conditions (40°C+), pot life can drop to 1–2 hours. Phenalkamine hardeners offer longer pot life in heat versus polyamide.
• Film thickness: Typically 50–75 microns DFT. Overapplication causes mud cracking; underapplication compromises protection.
• Humidity during application: Inorganic zinc requires humidity above 50% RH for proper cure — this can be a challenge in desert interiors of Saudi Arabia where RH drops below 20% in summer.

Sourcing These Raw Materials in the GCC

Raykem supplies liquid epoxy resins (Bisphenol A, EEW 182–192), polyamide and phenalkamine hardeners, reactive diluents, wetting and dispersing agents, and aromatic solvents (Xylene, Aromatic 100) to paint manufacturers across the UAE and Saudi Arabia. Our solvent portfolio includes IPA, n-Butanol, Xylene, and Toluene available in drums, IBCs, and bulk quantities with full SDS and COA documentation. Contact our technical team for formulation-specific product recommendations.