What Is Corrosive Sulphur?
Corrosive sulphur compounds are chemically active sulfur-based contaminants present in some transformer oils, especially those that haven’t been properly refined or aged. These compounds can react with copper to form copper sulfide (Cu₂S), a conductive and harmful deposit that degrades dielectric strength.
The Corrosive Sulphur Test identifies whether the oil contains compounds that could react under operational temperatures.
Test Standard
ASTM D1275, Method B – Standard Test Method for Corrosive Sulfur in Electrical Insulating Oils
Test Procedure Summary
- A polished copper strip is immersed in oil
- The sample is heated for 19 hours at 150°C
- Post-heating, the copper strip is visually examined for tarnishing or blackening
- Results are recorded as “Corrosive” or “Non-Corrosive”
Key Gases Measured
Insulating Liquids – Measurement of Relative Permittivity, Dissipation Factor (Tan δ) and DC Resistivity.
| Result | Interpretation | Action Required |
|---|---|---|
| Corrosive | Reactive sulphur detected | Immediate action: filtration or replacement |
| 100Non-Corrosive | No reactive sulphur present | Oil safe for use |
Why Corrosive Sulphur Testing Is Important
- Detects hidden risk to copper windings
- Prevents copper sulfide deposition
- Ensures compatibility with paper insulation
- Avoids premature failure and expensive outages
- Required for quality control of new and reclaimed oils
Our Testing Process
- Clean, vacuum-sealed sample collection with barcode tagging
- Heating and exposure of polished copper strip in controlled lab oven
- Visual and optical inspection for copper discoloration
- Fully compliant with ASTM D1275B procedural requirements
- Digital report generation with ERP-based traceability
Report Includes
- Corrosive sulphur result (Pass/Fail)
- Image of tested copper strip (optional)
- Notes on oil condition and safety for continued use
- Maintenance or filtration recommendations
- Regulatory compliance status (for new/reclaimed oils)
Why Choose Tru-FIL?
- ASTM D1275B-compliant and NABL-grade testing
- Expert chemists and temperature-controlled lab setups
- ERP-integrated reporting and AI-enhanced analytics
- Pan-India vacuum sample collection & 24/7 lab support
- Trusted by utilities, OEMs, and EPC contractors across India