[Ferro List] Part 2 /Tom's Crud/Passivisation

[Christopher Glasspool]

THIS IS PART 2
I have a book on Metal Lath by Gary J. Maylon, and I contacted him with questions on the perceived passivisation problem, and whether expanded metal lath was passivated from the manufacturer as I thought I had read. He said that in thirty years of forensic testing in stucco, he had never come across a problem of passivisation of the reinforcement, and that in properly executed stucco the bond was always intimate. He also said in the G60 cover of the expanded lath that not enough zinc was in that covering to cause a problem even if the potential of a passivisation problem was possible in his opinion. He knew of no specification for passivisation of expanded metal lath.
I found nothing about Natural Passivisation on the Internet, nor had Gary Maylon ever heard of it, and that will be one of the things I test for a difference in - Naturally Passivated and non-passivated metal lath. Martin Iorns was a smart guy, but on this he may have got it wrong. Natural Passivisation may or may not really exist, but in any case it appears not to be necessary according to all that I have read thus far.
If you look at the Material Safety Data Sheet on expanded metal lath you will see both oil and Chromium Trioxide listed in the possible list of ingredients and this is stated that either passivisation or oil may be used in cases of humid areas where storage stain or white rust may occur. I doubt however that you would find passivated product because the E.P.A. just in recent times expanded the toxicity of Chromium Trioxide to ten times of what had been previously thought, and now the material has been completely banned in Europe, under a recent agreement.
END OF PART 2, SEE PART 3


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