Anticorrosive protection for gas infrastructure faces particularly demanding operating conditions, characterized by high ambient humidity, recurrent condensation, and limitations in achieving completely dry surfaces. In this context, conventional coating systems often exhibit premature failures associated with surface preparation deficiencies or the inability to fully control moisture content during application.
The Protal™ 7300 coating has been designed to respond to these real operating scenarios, allowing its application on dry or controlled damp surfaces without compromising system performance, provided that the established technical criteria for preparation, application, and quality control are met.
Scope of Application and Protected Assets
This system is oriented towards the external anticorrosive protection of carbon steel in gas infrastructure. Its use is especially relevant on components exposed to permanent condensation, high humidity environments, and thermal variations, where absolute drying of the substrate is not always viable.
Typical assets:
- Pipelines and field joints.
- Branches and fittings.
- Valves and flanges.
- Prefabricated spools.
- Metering and regulation station bodies.
Surface Conditions and Acceptance Criteria
Protal™ 7300 can be applied on dry or damp surfaces, provided there is no visible free water.
- Acceptable damp surface: One presenting a thin film of moisture (typically from condensation) without drops, puddles, or running water. Practical verification is done using a dry cloth, confirming the absence of visible water transfer.
- Prohibited conditions: Surfaces wet with free water or frozen surfaces (ice, frost, or substrate < 0 °C / 32 °F).
During application, the work area must be kept free of visible water through continuous manual drying; post-application condensation does not invalidate the application if the initial criteria were met.
Surface Preparation and Anchor Profile
Surface preparation is a critical factor for system performance:
- Pre-cleaning: Removal of oils and grease per SSPC-SP 1.
- Mechanical preparation: Abrasive blasting to Near-White Metal (SSPC-SP 10 / Sa 2½).
- Anchor profile: Range of 2.5 to 5.0 mils, measured per ASTM D4417 (replica tape).
- Restricted areas: Localized preparation to bare metal (SSPC-SP 11) is permitted if total corrosion removal and an adequate mechanical profile are guaranteed.
Environmental Control and Application in Humid Conditions
Application requires continuous monitoring of relative humidity, ambient temperature, and dew point. The permitted substrate temperature range is 0 °C to 65 °C (32 °F to 150 °F).
To verify the absence of free water on vertical surfaces, the empirical practical criterion (Method V) is used. Under gas operating conditions, the system is formulated to cure in a humid environment, provided control is maintained during application.
Mixing, Application, and Thickness Control
Protal™ 7300 is a two-component system (base and hardener) with a mixing ratio of 2.5:1 by weight or 2:1 by volume. Being a 100% solids system, the wet film thickness is equivalent to the dry film thickness.
- Application methods: Brush, pad, roller, or airless equipment (depending on geometry).
- Stripe coat: Mandatory on welds, edges, and bolts.
- Recommended thickness: 20 to 70 mils (typical: 30 mils).
Application in Caribbean Zone (Critical Restriction)
Under typical conditions of the Caribbean Zone (temperatures ~30 °C and high humidity), the pot life of the mixture is reduced to approximately 10 minutes.
Under these conditions, it is recommended to:
- Limit maximum application area to: 1 m².
- Use minimum crews of two applicators.
- Ensure continuous application without interruptions longer than two minutes.
Final Inspection and Quality Control
The system will be accepted when it meets:
- Visual inspection (absence of defects).
- Dry film thickness within specification.
- Minimum hardness of 70 Shore D.
- Discontinuity detection (Holiday test): Only perform when the coating is fully cured and dry to avoid false positives.
Repairs and Localized Maintenance
Repairs will be classified by size, applying localized preparation via SSPC-SP 11 or abrasive blasting SSPC-SP 10. Repaired zones must present smooth transitions with the existing coating and meet application criteria again.
