Stainless steel angle beads

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wilmere

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I have a Victorian building - the windows were renewed 4 years ago and new plastering around the windows was done internally using stainless steel angle beads. On certain windows (on the right hand side only), the angle beads seem to have "rusted" and expanded cracking the plaster and in places, parts of the plaster have fallen off - this is accompanied with a brown rust-like stain.

Any possible explanations?
 
Hm, stainless steel has become galvanised - oh dear, I wondered if that may have happened.

I read somewhere that one should not mix stainless steel beads with gypsum based plaster - would that explain the problem?
 
wilmere said:
Hm, stainless steel has become galvanised - oh dear, I wondered if that may have happened.

I read somewhere that one should not mix stainless steel beads with gypsum based plaster - would that explain the problem?
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I think the suggestion is that they were never stainless steel in the 1st place hence the reason you are getting rust now!
 
give the wall a coat of kidology........like your plasterer did when the beads were put up.............and like 2 of my "oak" fence posts too :evil:
 
Even if your plasterer did use galvanized beads they shouldn't have rusted, especially seeing yo say these are internally.

I would be more concerned where the dampness is coming from, allowing the beads to rust.
 
I have checked the angle beads with a magnet and they are not magnetic, suggesting that they are in fact stainless steel - the plaster around them is dry although the bead itself is wet (smells like rust, looks like rust, but when wiped, the surface is shiny). Is there any other chemistry that would cause this?
 
JohnD said:
not all. Depends on the alloy.
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Stainless steel has a certain steel content that remains magnetic. If it isn't magnetic - then it isn't 'STEEL'.
 
John. Not all stainless alloys are stainless steel. From memory stainless steel has a added amount of chromium between 8 and 15 %. It is magnetic. Just because it is a stainless alloy doesn't mean it's stainless steel.
 
I can post you a stainless steel screw if you want, you can test it with a magnet.
 
JohnD said:
I can post you a stainless steel screw if you want, you can test it with a magnet.
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Stainless alloy. If it is steel then it is magnetic - if it isn't - it isn't steel.
 
a steel mill said:
"Austenitic stainless steels are non-magnetic. When nickel is added to stainless steel in sufficient amounts the crystal structure changes to "austenite". The basic composition of austenitic stainless steels is 18% chromium and 8% nickel. This enhances their corrosion resistance and modifies the structure from ferritic to austenitic. Austenitic grades are the most commonly used stainless steels accounting for more than 70% of production (type 304 is the most commonly specified grade by far). They are not hardenable by heat treatment.

Super austenitic grades have enhanced pitting and crevice corrosion resistance compared with the ordinary austenitic or duplex types. This is due the further additions of chromium, molybdenum and nitrogen to these grades. "
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