Which characteristic of water makes it more corrosive?

The characteristic of water that makes it more corrosive is low pH with dissolved gases. Water with a low pH indicates high acidity, which often results from the presence of dissolved gases such as carbon dioxide (which forms carbonic acid). This acidic condition enhances the water's ability to react chemically with metal surfaces and other materials, increasing the rate of corrosion.

When dissolved gases lower the pH, they can disrupt the protective layers that typically form on metals, leading to accelerated deterioration. This phenomenon is particularly significant in environments such as drinking water distribution systems and industrial processes where acidic water can lead to metal leaching and damage over time.

In contrast, high pH levels can make water less corrosive because alkaline conditions can stabilize protective scales on metal surfaces, while the presence of minerals can also form protective coatings, and high temperatures alone do not necessarily correlate with increased corrosiveness without the influence of acidity.