A cathodic protection survey is a field measurement programme that establishes whether a buried or immersed structure is actually protected, where it is not, and why. Surveys provide the design inputs for a new system, the acceptance evidence at commissioning, and the ongoing proof of compliance across an asset’s life. Without them, cathodic protection is an assumption rather than a demonstrated condition.
Corrpro Europe provides the full range of cathodic protection services covering testing, field surveys and audits, delivered by ICorr and AMPP certified engineers and technicians. We survey onshore pipelines, petrochemical plant, power stations, storage tanks, jetties and quay walls, offshore platforms, ships and vessels and immersed structures across the UK, Europe, the Middle East and Asia.
Our cathodic protection survey and testing services
Corrpro Europe carries out pre-design, baseline, operational and maintenance surveys. Each survey type answers a different question about the asset.
Close Interval Potential Survey (CIPS)
A Close Interval Potential Survey (CIPS) measures pipe-to-soil potential at close intervals along a pipeline route, typically every one to two metres, to build a continuous protection profile rather than a set of readings at test posts. It identifies under-protected sections, areas of overprotection and the effect of interference along the route.
CIPS uses synchronised current interruption so that both on and instant-off potentials are recorded. The instant-off reading removes the IR drop error, which is the most common reason a structure appears protected when it is not. A CIPS survey is used to validate a newly commissioned system, to investigate suspected under-protection, and as a periodic integrity check.
Direct Current Voltage Gradient (DCVG) survey
A Direct Current Voltage Gradient (DCVG) survey locates and sizes coating defects on a buried pipeline by measuring the voltage gradient in the soil above the line. Defects are graded by severity, usually as a percentage IR value, allowing an operator to prioritise excavation and repair on the defects that matter rather than digging speculatively.
DCVG and CIPS are complementary and frequently evaluated together. CIPS tells you where the pipeline is not adequately protected; DCVG tells you where the coating is compromised and how badly. Together they support External Corrosion Direct Assessment (ECDA) programmes.
Soil resistivity survey
A soil resistivity survey measures how current will flow through the soil surrounding a structure. Resistivity is the single most influential input into anode sizing and groundbed design, and it also indicates corrosivity: low-resistivity soils are generally more aggressive.
We measure resistivity across a route and can arrange full laboratory analysis of soil samples where chemistry, such as chloride or sulphate content, is relevant to the design or to a corrosion investigation.
Current attenuation and current drain surveys
A current attenuation survey measures how protective current decays with distance along a pipeline, indicating overall coating quality and identifying sections where current is being lost. A current drain survey quantifies current lost to other structures, foreign pipelines or earthing systems.
Both are diagnostic tools. They are used when a system is drawing more current than the design predicted, or when protection falls away at distance from the drain point, and they frequently reveal unintended electrical contact or a coating problem that no potential reading alone would explain. This survey can also be used to determine the current required to provide adequate cathodic protection (CP) for the asset.
AC and DC interference surveys
An AC interference survey quantifies alternating voltage and current induced onto a buried pipeline by nearby high-voltage power infrastructure. It matters for two reasons: elevated touch voltages present a safety risk to personnel, and AC-induced corrosion is highly localised and can occur at coating defects even where the CP potential criterion appears to be satisfied.
Our interference surveys include mapping powerline proximity using site survey and satellite imagery, measuring electromagnetic field (EMF) levels to infer operational load, and high-resolution data logging to capture steady-state and fluctuating conditions across varying operational states. DC interference surveys address stray current from HVDC cables, DC traction systems and other sources. For complex pipeline and energy corridor scenarios, including solar farm and battery energy storage system proximity, we use computer modelling to predict induced voltages across the full route before mitigation is designed.
For the wider technical background on interference and mitigation methods, see our AC interference in pipelines article.
Cathodic protection audit
A cathodic protection audit is a structured review of whether an existing CP system is performing as designed and meeting the requirements of the governing standard. It goes beyond a potential survey to examine the system as a whole: design basis, as-built condition, transformer rectifier performance, anode remaining life, test facility condition, monitoring records and compliance evidence.
Audits are typically commissioned when an asset changes hands, when an integrity case needs supporting evidence, when a system has been inherited without documentation, or when protection is failing and the cause is not obvious. The output is a clear statement of compliance status and a prioritised remediation plan. We also provide third-party design reviews and act as an independent reviewer of other suppliers’ CP systems.
Which survey do I need?
| Survey | Answers the question | Typically used |
|---|---|---|
| CIPS | Is the pipeline protected along its full length? | Commissioning validation, periodic integrity checks |
| DCVG | Where is the coating damaged, and how badly? | Defect prioritisation, ECDA programmes |
| Soil resistivity | How will current behave in this ground? | Pre-design, corrosivity assessment |
| Current attenuation / drain | Where is protective current being lost? | Diagnostics, higher than expected current draw |
| AC / DC interference | Is nearby infrastructure creating a safety or corrosion risk? | Power line corridors, HVDC, traction, solar and BESS proximity |
| CP audit | Is the whole system compliant and fit for purpose? | Asset transfer, integrity cases, inherited systems |
When do I need a cathodic protection survey?
You need a cathodic protection survey in the following situations:
- Before designing a new system, to establish soil resistivity, baseline potentials, continuity and interference exposure.
- At commissioning, to prove the installed system meets the protection criterion in the governing standard.
- On a routine cycle, to demonstrate ongoing compliance and detect degradation before it becomes metal loss.
- When protection levels fall, to locate the cause rather than simply increasing the transformer rectifier output.
- When new infrastructure appears nearby, particularly high-voltage lines, HVDC cables, solar farms or battery storage.
- When taking on an unfamiliar asset, where the CP system’s design basis and history are undocumented.
- Before an integrity case or regulatory submission, where evidence of protection is required.
Instrumentation and certified field technicians
Survey quality depends on the competence of the technician and the calibration of the instrument. Corrpro Europe’s field teams are ICorr and AMPP certified, and our surveys are carried out using industry-leading instrumentation from manufacturers we also distribute in the UK:
- M.C. Miller: corrosion engineering instrumentation for cathodic protection professionals, including potential measurement and survey data logging equipment.
- Tinker & Rasor: a Texas-based manufacturer of corrosion control instrumentation, including holiday detectors, Detectron pipe and cable locators and CP testing equipment.
- Borin Manufacturing: STELTH permanent reference electrodes and the DART and COMANCHE remote monitoring ranges, providing stable long-term potential data.
Because we distribute these ranges, we can also supply and support the instrumentation your own team uses. See our distributor and partner details.
Reporting: engineering analysis, not raw data
A survey report full of readings is not an engineering deliverable. Our reports interpret the data: what it means, whether the asset meets the protection criterion, where it does not, what is causing the shortfall, and what should be done about it, prioritised by risk.
Every report is produced against the relevant standard, most commonly ISO 15589-1 for onshore pipelines, ISO 15589-2 offshore, EN 12954 for buried and immersed structures, AMPP SP0169, or BS EN 50162 where stray current is involved. Reports are written to support integrity cases and regulatory submissions, and to be read by engineers who were not on site.
Assets and sectors we survey
Corrpro Europe carries out CP surveys and audits across onshore pipelines including river crossings, refineries and process plant, onshore terminals and tank farms, above-ground storage tanks, buried and mounded LPG vessels, power stations, jetties, wharfs and quay walls, steel piling, water treatment plant, offshore platforms and risers, ships and vessels, FPSOs and reinforced concrete structures including bridges and jetties. We also support offshore wind and solar infrastructure, where interference studies for solar piles and adjacent pipelines are an increasing requirement.
Frequently asked questions
What is a cathodic protection survey?
A cathodic protection survey is a field measurement programme that establishes whether a buried or immersed structure is receiving adequate protection. It provides the design inputs for a new system, the acceptance evidence at commissioning, and ongoing proof of compliance against standards such as ISO 15589-1 and EN 12954.
What is the difference between a CIPS and a DCVG survey?
A CIPS survey measures pipe-to-soil potential at close intervals to show whether the pipeline is protected along its full length. A DCVG survey locates and grades coating defects by measuring the voltage gradient in the soil above the pipeline. CIPS identifies where protection is inadequate; DCVG identifies where the coating has failed. They are complementary and are often evaluated together.
How often should a cathodic protection survey be carried out?
Frequency depends on the asset, its criticality and the governing standard, which sets inspection expectations. Routine potential monitoring is typically frequent, while full CIPS or DCVG surveys are carried out on a longer cycle or when triggered by a change in performance, a new interference source or an integrity requirement. We can define a monitoring regime appropriate to the asset and standard.
What is a cathodic protection audit?
A cathodic protection audit is a structured review of an existing system against its design basis and the governing standard. It examines design, as-built condition, transformer rectifier performance, anode remaining life, test facilities and monitoring records, and produces a compliance statement with a prioritised remediation plan.
Can you survey a cathodic protection system Corrpro did not install?
Yes. We regularly survey, audit and provide third-party design reviews of systems installed by others, including inherited systems with no documentation. Independent review is one of the more common reasons operators approach us.
Do you carry out AC/ DC interference surveys?
Yes. We quantify AC and DC interference through field investigation, powerline proximity mapping, electromagnetic field measurement and high-resolution data logging, and we use computer modelling for complex pipeline and energy corridor scenarios. We also design, supply and commission the resulting mitigation.
