Which of the following is NOT a test for soluble salts?

The standard conductivity test is not typically considered a specific test for soluble salts. Instead, it serves as a general method to gauge the conductivity of a solution, which can indicate the presence of dissolved ions, but it does not directly measure the types or concentrations of soluble salts present on a substrate.

In contrast, the Bresle Patch, Sleeve Test, and soluble salt meters are all specific methods designed to quantify soluble salts on surfaces prior to coating applications. The Bresle Patch method involves using a specific membrane to collect a solution that is then analyzed for salt concentration. The Sleeve Test, meanwhile, provides a means to sample the surface and measures the amount of soluble salts through a calibrated sleeve. Soluble salt meters are instruments specifically designed for measuring the concentration of soluble salts, providing a direct and fast assessment. Each of these methods has a defined protocol for accurately assessing soluble salt contamination on surfaces, crucial for ensuring proper coating adhesion and performance.