Rust on hot-dip galvanized balcony railing

[Magnus21]

I bought a hot-dip galvanized (and powder-coated) railing that arrived about a year ago. Gradually, some rust spots have actually appeared. In a couple of places where it rusts, it looks like scuffs on the metal, which were then painted over before installation. In some places, it looks like small holes. The contractor says the holes come from the galvanizing process, which requires holes in the construction.
I might just be able to fill those with some white sealant.

I'm more uncertain about these surfaces with rust. Perhaps the best is to scrub off the rust with some steel brush, but you don't really want to damage the remaining galvanizing with a steel brush so that you get even more rust in a few years. If I just paint over it, I would guess as an amateur that it will come back. Anyone have an idea about a reasonable measure for this?

 

[Alexn72]

Was it hot-dip galvanized before or after they were welded? I can't see any holes intended for draining the "galv" either. They should reasonably be handled through the pipes. How big are the holes?

 

[Magnus21]

First welded and then galvanized it is.

 

[Alexn72]

First welded and then galvanized it is.

If you haven't seen it yourself, I would say they are lying.

This metal part has been out maybe 5 years or if it's 10 years... With the damage in the picture... and nothing else done.

 

[Magnus21]

Oh, that was gloomy.

 

[plåtrickard]

If you haven't seen it yourself, I would say they are lying.

This metal part has been out maybe 5 years or if it's 10 years... With the damage in the picture... and nothing else done more.

The difference is probably that ts railing is also painted.

 

[Magnus21]

Was it hot-dip galvanized before or after they were welded
I can't see any holes meant for drainage of the "galv" either. They should reasonably be taken care of through the pipes. How large are the holes?

The holes are just a couple of mm large.

 

[Alexn72]

The holes are only a few mm in size.

Then I would doubt if they were galvanized when they were fully welded... possibly electrically galvanized but not hot-dip

 

[Berka81]

Then I would doubt if they were galvanized when they were finish-welded... possibly electro-galvanized but not hot-dip

I agree, there's no way it rusts through proper galvanization and then also a powder coating in such a short time.

Judging by the corner solution, it seems to be pipes in inch-dimension (so-called Vattenledningsrör or ISO pipes). These pipes are standard in pre-galvanized finish at most wholesalers. Therefore, I believe, just like others here, that pre-galvanized pipes were used, and then they ground down to bare steel to weld, then they simply painted everything and hoped for the best.

 

[Magnus21]

The rust is in areas where it looks like wear has occurred or some form of transport damage.

I thought there might have been damage to certain parts of the zinc coating.

The holes are too small to be holes for the galvanization, but the contractor has said that they plugged the holes from the galvanizing process with a bit of welding and that it wasn't completely sealed. That sounds like a reasonable explanation to me.

 

[Alexn72]

The rust is in places where it looks like there has been abrasion or some form of transport damage.

I thought there might have been damage to certain parts of the zinc coating.

The holes are too small to be holes for the galvanization process, but the contractor has said that they sealed the holes from the galvanization process with a bit of welding and that it wasn’t entirely sealed. That sounds like a reasonable explanation to me.

Welding on galv
For those curious, you can read a bit here about where the holes should be and their size
http://www.zinkenweland.se/sv-se/god_konstruktion/

 

[Dan_Johansson]

I think the color looks very unevenly thick to be powder coated.... It even looks like there are runs in some places, and I've never seen that on anything powder coated, not even at my friend's place who has equipment for a few thousand and does amateur coating in his garage....

 

[Magnus21]

Weld on galv
For the curious, you can read a bit here about where the holes should be and the size
[link]

Can't it be done?
Does anyone know if "weld metal" can rust?

 

[Stefan1972]

I hardly think that is hot-dip galvanized. Yes, holes are required for the process itself, but they are usually around 6-8mm and are left open afterwards. Why would you seal them? And no, you cannot weld holes shut once it is hot-dip galvanized.
I can imagine it is a railing that is welded together and then possibly powder-coated, but that never holds in exposed locations. The slightest bit of porosity allows rust to creep in and it comes off.

The damage is already done, so take a knife and scrape where it's rusty, and you'll see what's hidden there.

 

[roli]

Agree with the above post. That doesn't look galvanized. And if, as the manufacturer says, they welded shut the drainage holes from the galvanization (something that is rarely done), then that part is not galvanized and will rust quickly. Moreover, they've damaged the nearby galvanization during welding, so it doesn't protect the damage either. That's a poor job that isn't what they claim. Painting galvanized material requires expertise; the material to be painted should first age before painting or be blasted so that the paint adheres. There are probably more solutions, but it requires a knowledgeable executor to achieve a lasting result.