Buried · splash zone · submerged — the wet bands

No water, no cell: what a sealed end actually stops

Steel under backfill, a sawn pile top in the tide, a lead wire in a coke breeze bed: place the part in its band first, because a cap earns its keep only where standing water reaches metal.

Six ways a closed end opens again

There is no corrosion-sleeve range on this site

Four parts here bear on corrosion at all, and every one of them is a cap or an entry seal. Wraparound and tubular corrosion sleeves belong to a different family: heatshrink-sleeve.com. Nothing published here is a coating, a tape, a paste, a wrap or a cathodic-protection design service, and no page will pretend otherwise further down.

Four ingredients, and only one is yours to remove

An electrochemical cell runs when four things are present together: an anode area, a cathode area, a metallic path joining them and an electrolyte bridging the two. Three were settled long before you arrived, by the metal chosen and the way the assembly was built. The fourth is water with something dissolved in it, and it is the only ingredient a fitted part can take away. Take the electrolyte off the metal and the reaction is not slowed by some percentage; it has nowhere to run.

Which makes the barrier that almost works the interesting case. Water that finds its way under a lining cannot dry out, oxygen reaches one patch of that wetted area more freely than another, and those patches become the two halves of a cell with a very small anode and a very large cathode. Loss that would have spread thinly across an open surface now concentrates where the water sat. A pinhole is not nine-tenths of a seal; it is the geometry that turns even wastage into a pit.

So the question worth asking of a cap is not whether it keeps rain off. It is whether the lining has bonded to the substrate the whole way round the finished edge, and whether that bond survives the temperature swing the part will really see. Both lined constructions below are published as sealed to IP68, and both publish 0.2 per cent maximum water absorption for the material itself. Those are two claims about two different things, and the table keeps them apart.

One limit before the inventory: in air, none of this carries much weight. Dry metal in a switchroom is not corroding for want of a cap, so the barrier argument belongs to the three wet bands.

The complete inventory against a corrosion argument

Four parts. If what you are holding is not one of these, the useful answer is that this site does not hold it.

Buried · submerged

Hot-melt lined cap on a cable end

The lining softens under the torch, wets a jacket that is never truly round, and stays bridged to it as the part cools. Published to IP68 on XLPE, PVC, PILC and rubber-sheathed cable, codes GEC 001S to GEC 1101, diameters 2–4 mm up to 230–460 mm. It closes the end and only the end.

Buried · submerged

Mastic-lined cap on an anode lead wire

A rubber-based mastic asked to bond to two unlike materials at once, the anode body and the wire insulation, because that seam is exactly where the electrolyte must not reach. Codes GAC 0420 to GAC 0550, window −55°C to +100°C, sealed to IP68. See the manufacturer's anode cap page.

In air · splash zone

Hot-melt lined cap on a crown or a pile top

On a sawn timber top the adhesive runs into the checks and cavities as the cap comes down, so seal and reinforcement happen in one operation. Five sizes span 140 to 460 mm (5.5 to 18 in) of top diameter, on wood, concrete, steel or composite, with published service life beyond 30 years.

In air · splash zone

Heat-shrinkable gland where cable enters a box

Three pieces — an O-ring, a moulded heat-shrinkable body and a rigid nylon nut — with factory-applied hot-melt adhesive taking the seal onto the jacket. Pressure-sealed to 25 psi, rated 600 V, fume-tight. GHSG-1 to GHSG-5 accept cable of 5 mm to 67 mm.

The two lined caps, on the published numbers

Both are cross-linked polyolefin and both publish IP68 for the sealed construction. Read the corrosion row with care: it records that the cap material is non-corrosive, meaning it will not attack what it is fitted to. It is not a measure of how much corrosion the cap prevents, and neither sheet offers one. The cable-end figures come from the end cap datasheet.

Property	Anode cap (GAC)	Cable end cap (Insulcap GEC)	Test method
Lining	Rubber-based mastic	Hot-melt adhesive	—
Sealed rating	IP68	IP68	—
Corrosion	Non-corrosive	Not stated on the sheet	ASTM D2671
Water absorption	0.2 % max.	0.2 % max.	ASTM D570
Operating temperature	−55°C to +100°C	−40°C to +110°C	IEC 216
Shrink temperature	125°C	125°C	IEC 216
Low-temperature flexibility	No cracking at −40°C for 4 hrs	No cracking at −40°C for 4 hrs	ASTM D2671
Density	1.1 g/cm³ max.	1.05 ± 0.2 g/cm³	ASTM D792
Tensile strength	12 N/mm² min.	12 N/mm² min.	ASTM D638
Ultimate elongation	350 % min.	350 % min.	ASTM D638
Dielectric strength	12 kV/mm min.	12 kV/mm min.	ASTM D149
Size range	GAC 0420 to GAC 0550	GEC 001S to GEC 1101	—

Six lines that let a supplier answer in one reply

A barrier enquiry that omits any of these comes back as a question rather than a size code.

Substrate. XLPE, PVC, PILC, rubber, sawn timber, galvanised steel, concrete, a cast anode body. The lining is picked for what it must bond to, and mastic and hot-melt are not swappable.
Band. In air, splash zone, buried or submerged — and specifically the deepest band the part will ever reach, not the one it happens to sit in on the day the order is raised.
Diameter at the sealing face, in millimetres. Taken over the real jacket or the real sawn top, not lifted off a drawing. Ovality and armour ridges decide the fit more than the nominal figure does.
Temperature window in service. Published as −55°C to +100°C for the anode cap and −40°C to +110°C for the cable end cap. A part living outside either needs a different conversation, not a bigger cap.
Re-entry. A shrunk lined cap is permanent and comes off in pieces. If the end must be opened again for testing, say so before a part number is chosen: that one line moves the answer from a lined cap to a cover.
Whether a torch can be lit. A hot-work permit refused on the morning of the job is the commonest reason a correctly specified cap never goes on. The no-flame case has its own page.

What this page can and cannot answer

Is a heat-shrink cap corrosion protection?

Only where it removes the electrolyte from metal, and only across the area it covers. On a buried anode lead wire that area is precisely the one that fails, so the cap is doing corrosion work. On a pole crown it is doing rot and freeze-thaw work — water damage, but not an electrochemical cell. On a drum end under a dry roof it is doing neither, and is there for handling and contamination.

Do you supply corrosion protection sleeves or corrosion shrink wrap?

No. Caps and entry seals are the whole inventory here. A wrap that closes around a member already in place is a different geometry, failing at the overlap rather than at an edge, and that family sits on the site linked once at the top of this page.

The manufacturer's site has a page called corrosion-protection-tube. Is that a corrosion product?

No, and it is worth checking before anyone quotes from it. Two documents circulate under that corrosion-sounding filename and both publish the GTJ/2436 kV transition joint — the kit joining XLPE cable to PILC cable at 24 kV and 36 kV, with components matched across to paper insulation, lead sheath and steel armour, AC withstand 75 kV for one minute on the 36 kV series. It is a joint kit. A page built around that filename would publish a range that does not exist. The manufacturer's page shows what is in the kit.

What about switchgear and busbar corrosion?

A different problem answered by different parts. Metal going green inside a board is generally condensation and airborne contamination on exposed conductor, and what answers it is insulation over the bar and shrouding over the joint — fitted along the run, not at an end. No cap on this site addresses it.

Will a cap stop the anode itself from being consumed?

No, and it must not. An anode is installed to corrode; that is the point of the bed. What the cap seals is the joint where the lead wire enters the anode body — the connection the current must cross, and the place a bed commonly goes open circuit while the anode still has years of metal left.

Is a push-on PVC cap any use against corrosion?

It covers rather than seals, and that distinction is the whole page. It keeps direct weather and handling damage off a top or an end, and it can be pulled off and pushed back on, which no lined cap can. What it does not do is close the interface, so buried or immersed it behaves as the half-barrier above: it holds water against the metal instead of keeping it away.

Where the rest of this argument lives

Send the band, the substrate and one diameter

Three lines usually return a size code. Where nothing on this site fits the part you are describing, that is what comes back — there is no catalogue here to stretch over the gap.

What to put in the enquiry Read a size code before you quote it