Overview
ISO 11306:1998 provides international guidelines for exposing and evaluating metals and alloys in surface sea water. It defines practical procedures to obtain comparable marine corrosion data across different locations - from splash and tidal zones to depths where seawater composition resembles surface water. The standard emphasizes realistic exposure conditions, careful site selection, and systematic evaluation to assess corrosion performance in saltwater environments.
Key Topics and Requirements
- Scope and exposure duration
- Applicable to exposure zones from above sea level (splash/tidal) to shallow submersion; due to seawater variability, a minimum exposure greater than one year is recommended.
- Reference (control) specimens
- Use two types of controls: a known corroding material (e.g., mild steel) to gauge exposure severity and a corrosion‑resistant specimen (e.g., copper) to detect unusual contamination.
- Site selection and monitoring
- Choose representative, uncontaminated marine sites. Periodically record seawater parameters such as temperature, salinity, conductivity, pH, dissolved oxygen, tidal velocity and relevant chemical constituents.
- Exposure racks and fixation
- Racks must be non‑reactive for the exposure period. Materials cited include Monel 400 and coated aluminium or non‑metallic supports; avoid steel cables. Samples must be electrically isolated to prevent unintended galvanic cells.
- Specimen size, number and spacing
- Recommended minimum plate size: 100 mm × 300 mm; use duplicate or preferably triplicate specimens and plan intermediate removals (for example 6 months, 1 year, 2 years).
- Preparation and identification
- Remove oil/grease and mill scale per accepted practice; record mass, dimensions and surface condition before exposure. Mark specimens with corrosion‑resistant tags or coded notches.
- Evaluation and reporting
- Clean and remove fouling, weigh to about 1 mg precision, and calculate mass loss and corrosion rate (e.g., mm/year). Document localized attack (pitting, crevice corrosion, stress‑corrosion cracking) and include photographic records. Test reports must detail specimen metallurgy, surface preparation, exposure conditions and measured results.
Applications and Users
- Marine and offshore engineers assessing material selection for ships, platforms, coastal infrastructure and desalination systems.
- Corrosion laboratories and testing facilities conducting field exposure trials and lifetime predictions.
- Material suppliers, design offices and regulatory bodies needing standardized marine corrosion performance data.
Related Standards
- ISO 8407:1991 - Removal of corrosion products from corrosion test specimens (referenced).
- ISO 11463:1995 - Evaluation of pitting corrosion (referenced).
Keywords: ISO 11306, marine corrosion testing, corrosion of metals and alloys, surface sea water, exposure testing, corrosion rate, saltwater corrosion, test specimens, exposure racks.
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