What is one method used in wet lay-up to prevent corrosion?

In wet lay-up, hydrazine and morpholine are used as corrosion inhibitors to protect equipment, especially in marine environments. These substances help to maintain an alkaline environment in the system, which significantly reduces the likelihood of corrosion on ferrous and non-ferrous metals. The addition of hydrazine, in particular, acts as a reducing agent that helps to scavenge dissolved oxygen, which is one of the primary contributors to corrosion processes. Additionally, morpholine stabilizes the pH level, further ensuring that the environment remains conducive to corrosion prevention.

The other methods listed do not serve the same purpose or may not be effective in preventing corrosion in a wet lay-up scenario. For instance, while air purging can remove moisture and reduce oxygen, it doesn’t provide the chemical protection offered by hydrazine and morpholine. Sodium chloride addition would actually increase the risk of corrosion, and carbon dioxide injection, while sometimes relevant for other applications, does not effectively prevent corrosion in the way the correct answer does.