What does corrosion look like?
Red rust, white or grey powder, green deposits, flaking coatings and seized bolts — a slow attack that keeps spreading until its cause is removed.
Corrosion is the slow chemical or electrochemical attack on metal, taking an asset away from its design baseline. It shows as red rust on steel, white or grey powder on aluminium and zinc, green deposits on copper and brass, pitting, flaking coatings and seized or rounded fixings. Moisture, de-icing chemicals, salt air, dissimilar metals and failed coatings are the usual causes.
What matters is where it sits. A corroded current-carrying contact adds resistance, heats up and can flicker or open the joint. A corroded earth bond loses its protection silently, and only shows on the day insulation fails. Seized or rounded fixings let a fixture loosen and lose its seal, and a corroded break-away part may not break away as designed. Corrosion keeps spreading until its cause is removed, so treating only the visible part is not enough. Do not assume a corroded part is isolated or dead.
- Read the symptom. Rust, powder or green deposits, a flaking coating, seized or rounded fixings, or a flicker or earth-fault indication traced to a corroded joint.
- Isolate. Work under the permit-to-work; CCR off, locked out and tagged; prove the circuit dead. Never assume a corroded part is dead.
- Photograph as found. Before cleaning, with date and location, so the next inspection can show whether it is advancing.
- Judge what it is on and how far it has gone. A contact, an earth bond, a fixing or break-away part, or structure? Surface only, or material lost?
- Find the cause. The moisture path, de-icing chemicals, a dissimilar-metal contact or a failed coating — fix this or it returns.
- Act, re-test and record. Critical items first. Clean, protect and monitor surface corrosion; repair or replace where material is lost; re-test bonds and torque, and log the result.
The metal is marked but still does its job. Clean it, protect it, fix the cause and monitor it. See corroded condition.
Material is lost, or a contact, earth bond or break-away part is affected. Make safe first, then repair or replace.
Frequently Asked Questions
Q1What is corrosion in airfield lighting?
The slow chemical or electrochemical attack on the metal of an asset, taking it away from its design baseline. It shows as red rust on steel, white or grey powder on aluminium and zinc, green deposits on copper and brass, pitting, flaking coatings and seized or rounded fixings.
Q2What does corrosion look like on different metals?
Red rust on steel and iron, white or grey powder on aluminium and zinc, and green deposits on copper and brass. Beyond colour, look for pitting, a flaking or lifting coating, and fixings that are seized, swollen or rounded off.
Q3Why is corrosion of a contact or earth bond treated as critical?
A corroded current-carrying contact adds resistance, heats up and can flicker or open the joint, which on a series circuit can break the loop. A corroded earth bond silently loses its protective job, and the loss only shows on the day insulation fails. Corrosion of a structural or break-away part can change how it behaves under load. Critical items are made safe first.
Q4Why is cleaning the visible corrosion not enough?
Corrosion is progressive: it continues and spreads until its cause is found and removed. Cleaning the surface without fixing the moisture path, the dissimilar-metal contact or the failed coating lets it come back. Photographing it as found first lets the next inspection show whether it is advancing.
Q5What causes corrosion on airfield equipment?
Moisture, de-icing chemicals, salt air, dissimilar metals in contact and failed coatings are the usual causes. Water in cans and pits is the commonest feeder, so moisture ingress and corrosion are often found together.
Q6Is it safe to work on corroded equipment?
Work under the permit-to-work and do not assume a corroded part is isolated or dead. Isolate, lock out and prove the circuit dead before touching any lead, contact or bond, and follow the manufacturer's instructions.
See It. Understand It. Then Learn How to Engineer It.
Recognising an AGL system visually is the first step. The next step is knowing how to design, install, test, commission and maintain them correctly.
Build Practical AGL Engineering Skills
Go deeper with structured training from Precision AGL Academy, covering:
Learn how each light, sign and circuit works as part of a complete airport lighting system, not just as an isolated diagram.