Does unfinished steel used indoors in Bangkok, corrode?

[OneMoreFarang]

I like to use magnets to fix things on the walls.

First I though I will connect those magnets to stainless steel strips or screws. But then I learned that stainless steel, or at least most stainless steel, is not magnetic.

This is why I use now just ordinary steel, which is magnetic.

In some areas I use steel strips and they are painted to avoid corrosion.

My question is: Is it necessary to paint the steel or treat it otherwise to make sure there is no corrosion?

Or is the humidity in Bangkok indoors not really a problem in that way?

[scubascuba3]

Stainless Steel corrodes here along with Steel bolts and screws I've had

[Kwasaki]

How strong is your magnet. 

[Woof999]

It will rust almost certainly.

 

If the places you are hanging things are semi-permanent then consider embedding some pellet or coin shaped neodymium magnets in the wall. Ferrous metal will stick to the wall like magic, and/or other magnets (with the poles positioned correctly) will stick like glue.

 

The magnets will need to be embedded well into the wall, covered by at least 5mm or so of filler or they will pull out, especially if using another strong magnet on the thing you're hanging. Works well for my applications.

[OneMoreFarang]

6 minutes ago, Kwasaki said:

How strong is your magnet. 

Strong. Neodymium. Many of them.

[OneMoreFarang]

3 minutes ago, Woof999 said:

It will rust almost certainly.

 

If the places you are hanging things are semi-permanent then consider embedding some pellet or coin shaped neodymium magnets in the wall. Ferrous metal will stick to the wall like magic, and/or other magnets (with the poles positioned correctly) will stick like glue.

 

The magnets will need to be embedded well into the wall, covered by at least 5mm or so of filler or they will pull out, especially if using another strong magnet on the thing you're hanging. Works well for my applications.

Thanks

 

I (want to) use them for several things. With the wall I attached painted steel strips to the wall and the things which I connect use magnets. The reason it mostly that steel is a lot cheaper than the magnets. I can put the steel anywhere where I might want to connect something with magnets. I use the magnets only when I actually connect something.

[Woof999]

2 minutes ago, OneMoreFarang said:

Thanks

 

I (want to) use them for several things. With the wall I attached painted steel strips to the wall and the things which I connect use magnets. The reason it mostly that steel is a lot cheaper than the magnets. I can put the steel anywhere where I might want to connect something with magnets. I use the magnets only when I actually connect something.

Understood. I use these: https://www.thaiwatsadu.com/th/product/แม่เหล็กกลม-GIANT-KINGKONG-รุ่น-QJ7245-ขนาด-12-มม-(แพ็ค-6-ชิ้น)-60319377

 

plus the bullet type ones which don't seem to be on the site. Cheaper than they used to be.

[n00dle]

unless its in a moisture free vacuum unfinished steel everywhere corrodes.

[Kwasaki]

9 minutes ago, OneMoreFarang said:

Strong. Neodymium. Many of them.

Your into magnets you have lost me, the ones In bought on Lazada are rubbish. ????

[OneMoreFarang]

5 minutes ago, Kwasaki said:

Your into magnets you have lost me, the ones In bought on Lazada are rubbish. ????

I bought different types of magnets from this place.

https://www.lazada.co.th/shop/magnet-store/

They are strong - and expensive. 

[Kwasaki]

Just now, OneMoreFarang said:

I bought different types of magnets from this place.

https://www.lazada.co.th/shop/magnet-store/

They are strong - and expensive. 

I guess what I did was go cheap charlie . Thanks. ????

[OneMoreFarang]

2 hours ago, Kwasaki said:

I guess what I did was go cheap charlie . Thanks. ????

Did you?

I have to admit I looked for the physical size of magnets which would fit for my needs and then I ordered a few of them. I tested them and I thought they were "strong" for such small magnets.

I did not compare many sources and I don't know if there are big differences. So then I ordered as many as (I think) I need.

 

I had a little experience with modern magnets in brushless RC motors for quad copters. They use strong magnets and my new magnets behaved similarly.

If I would have found cheaper magnets from a supposedly decent source, then probably I would have tried them. Ali Express was a little, but not much cheaper, than buying in Thailand. 

[Kwasaki]

11 hours ago, OneMoreFarang said:

Did you?

I have to admit I looked for the physical size of magnets which would fit for my needs and then I ordered a few of them. I tested them and I thought they were "strong" for such small magnets.

I did not compare many sources and I don't know if there are big differences. So then I ordered as many as (I think) I need.

 

I had a little experience with modern magnets in brushless RC motors for quad copters. They use strong magnets and my new magnets behaved similarly.

If I would have found cheaper magnets from a supposedly decent source, then probably I would have tried them. Ali Express was a little, but not much cheaper, than buying in Thailand. 

I wanted more magnets for my motorcycle tank bag it was then I found something out when i ordered from Lazada. 

 

On Lazada I thought a bigger the circle the stronger the magnet as they were 20mm wide circle 2mm thick wrong,  it's the thickness that determines the strength it seems to me. 

The ones in my motorcycle tank bag are about 12mm wide circle but 4mm thick and are much stronger than the larger circle ones. 

[OneMoreFarang]

39 minutes ago, Kwasaki said:

I wanted more magnets for my motorcycle tank bag it was then I found something out when i ordered from Lazada. 

 

On Lazada I thought a bigger the circle the stronger the magnet as they were 20mm wide circle 2mm thick wrong,  it's the thickness that determines the strength it seems to me. 

The ones in my motorcycle tank bag are about 12mm wide circle but 4mm thick and are much stronger than the larger circle ones. 

I am sure it's the size and the thickness.

 

And the type of magnet. Neodymium magnets are much more powerful than "regular" magnets. And there are several subcategories of those Neodymium magnets.

 

 

 

 

 

[Kwasaki]

13 minutes ago, OneMoreFarang said:

I am sure it's the size and the thickness.

 

And the type of magnet. Neodymium magnets are much more powerful than "regular" magnets. And there are several subcategories of those Neodymium magnets.

 

 

 

 

 

Maybe my Honda tank bag has Neodymium ones. 

They small but strong.

 

The ones I bought lose strength because of the flap cloth layer before the tank.

I will get to change them. 

[brianthainess]

16 hours ago, OneMoreFarang said:

Is it necessary to paint the steel or treat it otherwise to make sure there is no corrosion?

Yes. Oil based silver paint or, red oxide both not expensive.

[sometimewoodworker]

22 hours ago, OneMoreFarang said:

If I would have found cheaper magnets from a supposedly decent source, then probably I would have tried them.

I have a lot salved from hard disks. They are almost certainly the bees knees of magnets.

[Damrongsak]

"Stainless" steel varies in its resistance to corrosion and magnetic properties.  Some stainless utensils are quite stainless and non-magnetic due to a high nickel content. I went around the kitchen and tested some spoons and ladles (mostly non-magnetic), the stainless stove (magnetic) and some other things.  Weirdest of all is the stainless sink.  It has magnetic and non-magnetic areas - probably because it has low nickel and has been work hardened in certain areas.

 

Magnets hold best if the steel surface is sufficiently thick for the particular magnet.  You may need a wider magnet on a thin sheet metal surface (like a refrigerator). A taller magnet may  be needed to hold up many sheets of paper. 

 

I have a few of those hard drive magnets.  They are very powerful.  Bought some surplus from a used equipment seller at a market in BKK years ago.  Down by Yaowarat/Pahurat.  Also got a few from tearing apart old drives from a file server.

[Yellowtail]

Hot-rolled steel typical has a grey/black coating of mill-scale which is reasonably rust resistant. Cold-rolled steel is silver, and uncoated, generally rusts quickly and easily.

 

Hot-roll is cheaper and more readily available. Hanging on a wall indoors I it will not rust quickly. You may want to wipe it down with a little Sonax or whatnot now and then. If you're after an industrial kind of look it would be perfect. 

 

Hot-dipped galvanized steel might be your best choice, it will not rust, and you can get it in high, low or no-spangle, and would give you a more high-tech look. I love the high-spangle look and did my office ceiling in it using all drop.

 

Stainless is too shiny in the thinner sheet for a wall, bedroom ceiling maybe... 

 

The sell the white-boards that will hold a magnet as well... 

 

[Lacessit]

1 hour ago, Yellowtail said:

Hot-rolled steel typical has a grey/black coating of mill-scale which is reasonably rust resistant. Cold-rolled steel is silver, and uncoated, generally rusts quickly and easily.

 

Hot-roll is cheaper and more readily available. Hanging on a wall indoors I it will not rust quickly. You may want to wipe it down with a little Sonax or whatnot now and then. If you're after an industrial kind of look it would be perfect. 

 

Hot-dipped galvanized steel might be your best choice, it will not rust, and you can get it in high, low or no-spangle, and would give you a more high-tech look. I love the high-spangle look and did my office ceiling in it using all drop.

 

Stainless is too shiny in the thinner sheet for a wall, bedroom ceiling maybe... 

 

The sell the white-boards that will hold a magnet as well... 

 

Unless the OP wants armor plating, hot rolled steel is too thick. IIRC, minimum thickness 2.2 mm, therefore heavy. The oxide layer is not stable indefinitely.

Zinc/aluminium alloy ( Zincalume or Galvalume ) has a uniform silvery spangle. Cheaper than painted, but subject to fingerprint blackening.The OP has already posted he is using painted steel.

 

Edited March 28, 2023 by Lacessit

[Yellowtail]

10 hours ago, Lacessit said:

Unless the OP wants armor plating, hot rolled steel is too thick. IIRC, minimum thickness 2.2 mm, therefore heavy.

You recall incorrectly about the thickness but yes, steel is heavy. 

SPCC Hot rolled coil_Shandong Bailiyuan Metal Manufacturing Co., Ltd. (blymetal.com)

10 hours ago, Lacessit said:

The oxide layer is not stable indefinitely.

Is anything stable indefinitely?  It has not been my experience that comes off easily. Indoors, on a wall, occasional wiped with Sonax or whatnot it would be fine, if one wanted the industrial look. 

10 hours ago, Lacessit said:

Zinc/aluminium alloy ( Zincalume or Galvalume ) has a uniform silvery spangle. Cheaper than painted, but subject to fingerprint blackening.The OP has already posted he is using painted steel.

That's what I would call no-spangle and it also stains. Low spangle looks something like silver hammer-tone paint, and it does not stain as easily. High-spangle looks like what people usually think of when they hear galvanized. I think this would be ideal as it wont chip, rust or stain. You can write on it with a marker and it cleans right off with acetone.

 

The bummer about paint is not only that it chips and wears off, but that markers and whatnot will stain it. 

 

The only thing you have to be careful of with galvanized is white rust, but this would be visible by the time the OP got it. 

[OneMoreFarang]

Thanks for all your info.

From the look of it my contractor installed hot rolled steel and painted it. I didn't measure it, I think it's about 2mm thick.

In my case all of this won't be visible once all is installed.

[Yellowtail]

6 minutes ago, OneMoreFarang said:

Thanks for all your info.

From the look of it my contractor installed hot rolled steel and painted it. I didn't measure it, I think it's about 2mm thick.

In my case all of this won't be visible once all is installed.

Nice! That was quick, I hope you love it. 

[Lacessit]

5 hours ago, Yellowtail said:

You recall incorrectly about the thickness but yes, steel is heavy. 

SPCC Hot rolled coil_Shandong Bailiyuan Metal Manufacturing Co., Ltd. (blymetal.com)

Is anything stable indefinitely?  It has not been my experience that comes off easily. Indoors, on a wall, occasional wiped with Sonax or whatnot it would be fine, if one wanted the industrial look. 

That's what I would call no-spangle and it also stains. Low spangle looks something like silver hammer-tone paint, and it does not stain as easily. High-spangle looks like what people usually think of when they hear galvanized. I think this would be ideal as it wont chip, rust or stain. You can write on it with a marker and it cleans right off with acetone.

 

The bummer about paint is not only that it chips and wears off, but that markers and whatnot will stain it. 

 

The only thing you have to be careful of with galvanized is white rust, but this would be visible by the time the OP got it. 

I don't think I recalled incorrectly, having worked for an Australian steel manufacturer for more than 30 years. Hot rolled, cold rolled, coated and painted.

The link you posted shows photos of hot-rolled and cold-rolled coils.

0.2 mm is tinplate, if anyone is making hot-rolled in that thickness I will bare my bum in the nearest shopping mall. 60 mm goes on tanks.

Mill scale is stable at humidities of < 60%, permit me to doubt it would be as good at 90%, which I would say is quite common in Bangkok.

Edited March 29, 2023 by Lacessit

[Yellowtail]

21 minutes ago, Lacessit said:

I don't think I recalled incorrectly, having worked for an Australian steel manufacturer for more than 30 years. Hot rolled, cold rolled, coated and painted.

The link you posted shows photos of hot-rolled and cold-rolled coils.

0.2 mm is tinplate, if anyone is making hot-rolled in that thickness I will bare my bum in the nearest shopping mall. 60 mm goes on tanks.

Mill scale is stable at humidities of < 60%, permit me to doubt it would be as good at 90%, which I would say is quite common in Bangkok.

Yeah, me with only forty years of fabricating experience, the last twenty of it in Thailand.

 

Look at the website again. the spec was for hot-roll. 

 

Benchtops from hot-roll I built in Thailand, for the plant in Thailand still holding up fine after over twenty years. 

 

 

 

 

 

 

[Lacessit]

10 hours ago, Yellowtail said:

Yeah, me with only forty years of fabricating experience, the last twenty of it in Thailand.

 

Look at the website again. the spec was for hot-roll. 

 

Benchtops from hot-roll I built in Thailand, for the plant in Thailand still holding up fine after over twenty years. 

 

 

 

 

 

 

The spec said 0.2 - 60 mm, 0.2 mm is NOT hot-rolled. Have you ever seen the manufacturing process for hot and cold rolled steel?

I can accept mill scale is holding up OK according to you.

Is that 40 years' experience, or one years' experience repeated 40 times?

[Crossy]

As our OP has his answer and the bickering has started.