Sealing a 0.5mm Hole in Leaking Cast Iron Radiator: Effective Solutions for Moist Conditions

Cast iron radiator - use to seal a leaking hole of 0.5 mm. There is moisture all the time, so it's harder.

You will have a hard time if there is moisture there. If you would try to dry this place somehow, you will find a lot of glue with which you can patch it up

EPOXY RESIN 7706 and N28 glue. The first one is about PLN 25 per package (2x12ml), the second one is about PLN 700 per 100ml. Adhesive 7706 can be used on damp surfaces.
Greetings

rafik108 wrote:

... sticks a lot with which ...

glue is plural to glue

If sealing helps, then good. Nevertheless, this is only an emergency repair. The proper repair can be done after draining the water from the installation (at least from this radiator). Is it leaking from the connection between individual ribs (this is the most common) or from the rib itself (such failures occur VERY RARE)? In the first case (leakage between the joints of the ribs), this leaky joint must be unscrewed (note: a special wrench is required and may require enormous force, especially after several decades of operation), replace the gasket in the lower and upper intercostal joints (after cleaning both ribs), turn the with radiator nipples (if the nipples were heavily corroded, they must be replaced). If a specific radiator rib is damaged, you have to unscrew it from the radiator and replace it with an undamaged one, and if the radiator is large (larger than necessary) - simply remove it from the set. Sometimes the radiators are oversized - especially when the building has been thermally insulated and the windows are replaced with tight ones.

For me, a similar problem, but specific because the radiator started to leak after painting, previously it was only yellowed, but there was no rust or leakage. The place is a joint between the last rib and the pipe, so I don't think about drilling or gluing. It's as if the paint has dissolved the bonding ...
Photos with a cell of a slightly poor quality because it's dark there ...

Do you think something can be done about it?

If I can see it correctly, it's leaking on the gasket. I don't think you can do without removing the radiator. A ring key probably 32 mm, heat it well with a burner. After unscrewing, clean it and give a new gasket.

The key is larger than 32 mm. If it is an old shell, it is even 48 mm, in newer ones a bit smaller (probably 42 mm), but you can always use a "Swede" (a large one). Of course, the water must be drained from this heater. Unscrew the plug, thoroughly clean the edge of the rib to which the plug is screwed in (clean the plug too, or give a new one), give a new gasket, which is also good to lubricate the so-called the liquid gasket (special sealing silicone, red) and screw it STRONGLY. You do not need to use tow for the thread (because it is cylindrical and they can slip), but you can - saturated with good thread paste or linseed varnish. The heater does not need to be removed for this. If the cap cannot be unscrewed, take a striking ring spanner (with such an anvil) and tapping the spanner unscrew it. Note the direction of the thread. Blind plugs usually have a left thread, while plugs to which the supply valve and the return pipe are screwed - right (if the radiator is cross-connected, the plug with the return screw connection is left).

What is this gasket that made the alkyd paint dissolve from? Where can you get such a gasket? Now it is after the heating season, I live in a skyscraper, do you think that the water is only in the radiators or in the entire system? I'm afraid of flooding myself and my neighbors!

Don't play repairs or you'll be making trouble for yourself. The water should be drained or frozen (special device). I've seen two supposedly experienced plumbers replace the plugs with one with a vent. They had a burner, they had a key (almost a meter long), a hammer of course. The heater practically almost jumped when they were processing it (one was holding a heater that was normally attached to the wall). Result - they replaced the plugs in 4 heaters, on the second day two heaters started to leak on connectors (the overloads were too high). The fact is that the radiators were 35 years old. Why do you want to do this? If you live in a block of flats, let the cooperative or the manager (housing association) do it. They charge the rent to the renovation fund. You cannot voluntarily flush the system without the consent of the building manager.

First you need to check if the water is drained from the system. In principle, the water should not be drained (it is better for the installation when it is constantly full), but some cooperatives do discharge so that someone does not flood during some repair. The gasket must be purchased in the store. As for unscrewing the plugs, last summer I removed the plugs from the radiators that were 48 years old (and replaced them with plugs with an opening to give air vents) using a 45 cm long "Swede". I had a problem with only one stopper and I had to use the wrench to beat. After replacing this plug, it is also worth tightening the screw connections, because overloads can actually loosen them (unseal).