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05-18-2015, 01:12 PM #1
Help Identify Substance on Metal Door Frame
Commercial building inspection. Aluminum door frame and threshold. Bottom of door frames are rusting and threshold is showing signs of deterioration. This white substance was built up in several areas. Could it be leftover ice melt? It was the consistency of wet laundry detergent. Thanks.
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05-18-2015, 03:28 PM #2
Re: Help Identify Substance on Metal Door Frame
Probably aluminum oxide or whatever corroding aluminum makes when the aluminum corrodes into that stuff.
Those are most likely aluminum, not steel, so it would be corrosion, not rust ... but ... I guess "rust" is a type of "corrosion" ...
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05-18-2015, 08:00 PM #3
Re: Help Identify Substance on Metal Door Frame
Yes, ice melt salt will do exactly what you have in the photos.
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05-19-2015, 05:24 AM #4
Re: Help Identify Substance on Metal Door Frame
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05-19-2015, 05:36 AM #5
Re: Help Identify Substance on Metal Door Frame
If it came from the aluminum, you'll see deterioration of the aluminum. I lean toward salt. Salt doesn't get washed out from the edges of the frame as easily and since salt "attracts" moisture, there can be efflorescence along the edge of the frame over time. Aluminum oxide is usually like talc in my observations and not as coarse as detergent.
If you choose not to decide, you still have made a choice.
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05-19-2015, 02:39 PM #6
Re: Help Identify Substance on Metal Door Frame
Could also be Urea or Calcium Chloride, both of which are deicing products.
Calcium Chloride is also used for dust control on dirt roads to keep the dust down and harden the surface.
And Urea is also a fertilizer.
FWIW.
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05-20-2015, 03:57 AM #7
Re: Help Identify Substance on Metal Door Frame
Iron oxidizes (rust).
Aluminum oxidizes too. In the form of a dull whitish patina that covers the material. The haze then protects it from further oxidation. Same thing with silver (tarnish), brass, etc.
When we polish these metals, the black that dirties the rag is the oxidation.
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05-20-2015, 06:09 AM #8
Re: Help Identify Substance on Metal Door Frame
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05-20-2015, 07:38 AM #9
Re: Help Identify Substance on Metal Door Frame
Thank you gentlemen!
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