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    Mineral Salts Chemical Explanation

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    What is the chemical explanation as to why salts of water borne minerals scale on the inside of water piping, specifically carbon steel or stainless steel piping?

    I know that more alkaline pH will produce many calcium, aluminum, iron, sodium, and magnesium salts in water systems.

    But is there a particular pH range in which one of these mineral salts will be more prevalent than another? And what exactly is the mechanism that physically causes the scale to actually build-up and attach to the inside of a pipe? Is the some type of electro-potential difference kind of scenario.? Would aluminum salts tend to scale more so thatn calcium or magnesium salts?

    I hope you can provide me a good detailed explanation ---- thank you so very much in advance. I want to learn and know as much as I can on this subject.



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    Solution Preview

    Scaling introduction
    All sources of natural water contain concentrations of dissolved mineral salts, primarily based on the bicarbonates of metals such as calcium, magnesium and iron bicarbonates. Within a stainless steel tank or piping system, at increased temperature these bicarbonates readily decompose and disproportionate into their respective calcium, magnesium and iron carbonate salts. These carbonate salts are sparingly soluble in water, even at increased temperature, when compared to the bicarbonates.
    As these carbonates excess carbonates form, precipitation occurs which subsequently become hard, rigid deposits. Mineral deposition primarily occurs on heat transfer surfaces in a system (but can occur elsewhere). These depositions act as insulators, lowering the heat transfer coefficient across the system, which consequently reduces the heat transfer capability of the material in question. This can lead to significantly increased fuel consumption and fuel costs and frequent maintenance costs - the effective insulating properties of these scale deposits ultimately result in metal surfaces experiencing excessive temperatures, causing them to crack, blister, or fracture. In less controlled and maintained cases, complete system failure can occur. Such mineral deposits are therefore a serious concern in a number of industries and novel technologies for inhibiting or clearing scale are constantly under investment. Damages and efficiency losses, as a result of scaling, especially with reference to piping infrastructure systems (typically stainless steel or analogous alloys) can be the source of major financial losses for a large number of industries worldwide.
    Metal Salts in Water
    • The key factors here are temperature and solubility
    The temperature at which the water in a system is maintained directly influences how well different salts dissolve and how long they can stay dissolved. Some salts are more soluble at higher temperatures whereas others are more soluble at lower temperatures. Other salts can remain dissolved while the water is at a relatively lower ...

    Solution Summary

    The expert determines the chemical explanation as to why salts of water borne minerals scale on the inside of water piping specifically carbon steel or stainless steel piping.