ISO 12944 C3 Medium Corrosion Coating System

Environment Definition

ISO 12944 C3 represents medium atmospheric corrosivity. It is common in urban and industrial atmospheres with moderate sulfur dioxide pollution, moderate humidity, or indoor production areas with higher moisture.

Typical examples include urban steel structures, general industrial workshops, food processing areas, machinery frames, and inland infrastructure not exposed to high marine salt.

Coating Selection Logic

C3 is often the point where a true protective coating system becomes more important than a simple decorative primer/topcoat. Epoxy primers and epoxy MIO intermediate coats are commonly reviewed for stronger barrier protection, while polyurethane or acrylic polyurethane topcoats are used when exterior gloss and color retention matter.

If the project has coastal salt, chemical fumes, splash exposure, or long maintenance intervals, review C4 or C5 instead.

Starting System Pattern

Layer	Typical role	Notes
Surface preparation	Abrasive blasting is preferred for new steel	Confirm blast grade, surface profile, and soluble salt control for the project.
Primer	Epoxy anti-corrosion or zinc-rich primer	Select zinc level and compatibility based on durability target and topcoat system.
Intermediate	Epoxy MIO or high-build epoxy coat	Adds barrier thickness and improves long-term protection.
Topcoat	Polyurethane, acrylic polyurethane, or compatible industrial finish	Choose for UV, color, gloss, and weather resistance.

Technical Review Points

• Confirm whether the exposure is indoor industrial, urban outdoor, or sheltered outdoor.
• Define expected durability range and realistic maintenance access.
• Confirm dry film thickness by layer instead of relying on product family names alone.
• Verify current Qilu Paints TDS/SDS, mixing ratio, pot life, and recoat interval before quotation.

Related Qilu Paints Products

• Epoxy Zinc-rich Primer (2K)
• Universal Epoxy MIO Intermediate Coat
• Aliphatic Acrylic Polyurethane Topcoat (2K)