What types of soluble salts are typically considered as contamination?

The correct answer identifies sulfates, nitrates, and chlorides as types of soluble salts that are typically considered contaminants in coatings applications. These salts can affect surface preparation and coating performance, leading to poor adhesion, resulting in compromised protective qualities of the coating.

Chlorides are particularly problematic because they can cause corrosion and negatively impact the bonding of the coating to the substrate. Sulfates can lead to similar issues, especially in environments where acidic conditions are present, and they can also affect the structural integrity of the surfaces they contaminate. Nitrates, on the other hand, can alter the chemical balance on the substrate surface, potentially leading to adhesion failures.

In contrast, the other choices include combinations of salts that are not predominantly recognized as contaminants or are less impactful. For example, phosphates are often used as pre-treatment processes to inhibit rust and promote adhesion rather than harm the coating application. Similarly, carbonates and hydroxides might have different roles and are less frequently singled out as significant concerns in the context of soluble salt contamination.