Standard · Metallic coatings and cathodic protection
NACE SP0169
Controlling external corrosion on buried or submerged metallic piping.
SP0169 is the long-standing practice for protecting buried and submerged pipelines with coatings and cathodic protection together: design, criteria, installation, monitoring and records. AMPP sells it as NACE SP0169-2024.
The two criteria for steel
- At least 100 mV of cathodic polarization, measured as it forms or as it decays.
- A potential of −850 mV or more negative against a copper/copper sulfate electrode (CSE). It is measured as a polarized potential, or with the current on. With the current on, voltage drops other than across the steel–soil boundary must be considered.
Special conditions can need more. With microbial corrosion or no oxygen, −950 mV may be needed; above 60 °C, −950 mV or more negative.
More negative is not always better
Too much current makes the steel surface highly alkaline, which weakens coating adhesion, and makes hydrogen, which can embrittle steel. The standard sets no fixed limit, because the risk varies. For the inspector, this is the link between CP and cathodic disbondment of the coating.
Common mistake
Writing "AMPP SP0169". The name keeps the NACE prefix.
1 practice item in the members area mentions NACE SP0169 (CIP 2: 1).
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This page describes the subject of NACE SP0169 in our own words; it does not reproduce the standard. For the full text, buy the current edition from AMPP. Checked on 2026-10-14; errors go in the corrections log. CoatMentor is an independent study aid. It is not affiliated with ISO, AMPP, SSPC, NACE International, ASTM or FROSIO.