The preferred fix is to separate bare brass or copper from the aluminium enclosure with a compatible plated gland and the sealing arrangement approved for the Ex assembly. Nickel- or tin-plated glands address the metal interface directly. Silicone grease may slow electrolyte entry, but it does not replace compatible materials, a certified seal, or a verified bonding path.
What is the enclosure interface telling you?
Start at the cable entry, because the first signs usually appear there: white aluminium corrosion product, green or dark staining near brass or copper, pitting around the entry hole, a lifting washer, damaged coating, or a seal that no longer seats evenly. Record whether the enclosure is outdoors, washed down, exposed to salt or chemicals, or subject to condensation. Galvanic attack needs electrically connected dissimilar metals and an electrolyte; removing any one of those conditions interrupts the corrosion cell.
| Observation | Check location | Likely significance |
|---|---|---|
| White deposits or pitting | Aluminium around gland entry | The aluminium may be acting as the less noble metal in a galvanic couple. |
| Green or dark deposits | Brass gland or copper washer | Moisture has reached the dissimilar-metal interface. |
| Dry, clean joint | Under washer and thread entry | No visible attack now; material compatibility and sealing still require review. |
| Loose or uneven washer | Gland shoulder and enclosure wall | The seal may admit moisture and the bonding contact may be unreliable. |
Clean only enough surface to inspect it without removing sound enclosure material or altering the cable-entry geometry. If pitting has changed the sealing face, thread form, or wall thickness, refer the enclosure to its manufacturer before reuse. The check passes when the metal interface, coating condition, and environmental exposure are documented.
Which metals are actually touching?
Trace every conductive layer from gland body to enclosure: gland plating, exposed base metal, locknut, sealing washer, earth tag, thread, enclosure coating, and bare aluminium. A copper sealing washer against aluminium creates a direct dissimilar-metal interface. Bare brass against aluminium creates another. Moisture in either joint completes the electrochemical path.
The useful distinction is between plating and grease. Nickel or tin plating changes the surface metal presented at the joint and is recommended for this application by Pirelli and Hawke. Grease is a barrier material: it can exclude some water while intact, but assembly pressure, thread motion, temperature cycling, and maintenance can displace it. It cannot correct an exposed copper washer or damaged plating.
| Configuration | Location | Effect |
|---|---|---|
| Nickel- or tin-plated gland | Gland body and threaded interface | Reduces direct exposure of bare brass at the aluminium joint when the plating remains intact. |
| Bare brass gland | Thread and gland shoulder | Leaves a dissimilar-metal couple wherever brass contacts aluminium. |
| Copper sealing washer | Between gland and enclosure | Adds a copper-to-aluminium interface and can concentrate attack at exposed aluminium. |
| Silicone grease | Threads or sealing interface | May restrict moisture ingress but does not change the underlying metal pair. |
The check passes when the gland, washer, locknut, and enclosure contact surfaces are identified by material rather than appearance alone.
Is the proposed gland valid for the Ex assembly?
Material compatibility is only one decision. The gland must also match the cable construction, cable diameter, entry thread, enclosure entry method, environmental sealing requirement, and the protection concept used by the Ex equipment. Read these details from the gland documentation, enclosure marking, entry schedule, and approved assembly instructions; the evidence provides no specific protection concept or hazardous-area approval.
Do not substitute a nylon gland merely to eliminate a metal couple. A nonmetallic gland changes mechanical retention, sealing, static control, earthing, and fault-current behavior. Use it only when its approval and the equipment instructions permit that exact type of entry.
Grease receives the same treatment. Confirm that the enclosure or gland manufacturer permits the compound at the threads or sealing face. Check chemical compatibility with the elastomeric seal, cable sheath, plating, coating, and expected temperature. A compound that attacks a seal or prevents the designed metal contact can create a larger fault than the corrosion treatment solves.
The check passes when the selected gland and every added washer, adaptor, seal, and compound are allowed by the documented Ex configuration.
How should the cable entry be assembled?
- Isolate the equipment under the site electrical procedure and confirm the entry can be opened without violating hazardous-area controls.
- Remove corrosion products, old compound, and debris using a method accepted for the enclosure. Do not enlarge the hole, reshape threads, or abrade away sound plating.
- Inspect the aluminium sealing face and thread for pitting. Inspect the gland plating for scratches, flaking, or exposed brass. Replace damaged components rather than covering damage with grease.
- Replace a direct copper-to-aluminium sealing arrangement with the compatible, documented sealing hardware specified for the gland and enclosure.
- Install the approved nickel- or tin-plated gland with the required locknut, sealing washer, earth tag, or adaptor. Apply only a manufacturer-permitted compound, and only at the stated location.
- Tighten the entry and cable seal using the manufacturer’s assembly method. Avoid improvised torque values; read the required value from the applicable gland instructions.
- Dress and support the cable so weight, bending force, and vibration do not load the gland or disturb the seal.
The check passes when the gland sits square, the seal is uniformly compressed, no bare brass or copper contacts exposed aluminium, and the cable cannot transfer movement into the entry.
Does corrosion control preserve bonding and sealing?
Do not treat a visually sealed joint as electrically proven. Paint, oxide, grease, insulating washers, and nonmetallic glands can interrupt a bonding path. Determine whether the design bonds the cable armour or gland through the enclosure wall, through an earth tag, or through a separate conductor. Then test that intended path using the site-approved continuity method and acceptance criterion.
Also inspect the environmental seal independently. A thread compound may fill thread clearances while leaving the shoulder washer incorrectly seated. Conversely, a sealing washer can exclude water while the internal armour termination remains loose. Verify both the enclosure boundary and the cable termination.
| Test | Location | Passing result |
|---|---|---|
| Visual alignment | Gland shoulder and entry face | Square seating with no gap, distortion, or trapped debris. |
| Cable retention | Cable immediately outside gland | No movement at the termination during the approved retention check. |
| Bonding continuity | Across the intended protective path | Meets the project’s documented acceptance criterion. |
| Seal inspection | Washer, thread interface, and cable seal | Correct components, even compression, and no visible leakage path. |
The check passes only when corrosion protection, bonding, and sealing work together; grease alone proves none of them.
How is the repair verified end to end?
- Record the enclosure, entry location, gland material or plating, washer type, and any permitted compound used.
- Photograph the clean interface before assembly and the completed entry afterward so later inspections can distinguish new attack from old staining.
- Complete the required bonding, cable-retention, and enclosure-seal checks. Record the instruments, method, and acceptance criteria used by the project.
- Return the equipment to service under the site procedure and inspect the entry after its first relevant exposure, such as rain, washdown, or a condensation cycle.
- Add the interface to the hazardous-area inspection schedule. Compare later photographs for fresh deposits, coating lift, plating damage, pitting, loose hardware, or moisture tracks.
The end-to-end check passes when the approved entry remains mechanically secure, electrically bonded as designed, sealed against its environment, and free of new corrosion.
Frequently Asked Questions
How do I prevent brass cable glands corroding an aluminium enclosure?
Use a documented Ex-compatible gland with nickel or tin plating, remove direct copper-to-aluminium contact, maintain the environmental seal, and preserve the intended bonding path.
How do I know whether silicone grease is acceptable on Ex gland threads?
Check the gland and enclosure assembly instructions for permission, application location, and material compatibility. Grease is not a substitute for compatible plating or approved sealing hardware.
How do I inspect galvanic corrosion at a cable entry?
Look for white deposits and pitting on aluminium, green or dark staining near brass or copper, damaged plating, coating lift, uneven washers, and moisture tracks beneath the gland.
How do I use a nylon gland instead of a brass gland?
First confirm that the gland approval, protection concept, cable construction, mechanical retention, sealing, and earthing arrangement permit a nonmetallic entry. Do not make the substitution based only on corrosion resistance.
How do I verify the completed Ex cable-gland repair?
Inspect seating and cable retention, test the documented bonding path, verify the enclosure seal, record the installed materials, and confirm at the next inspection that no fresh deposits, pitting, looseness, or moisture tracks have appeared.