Leaving a cast iron pan in a vinegar bath for an extended period of time can cause damage to the pan and potentially affect its safety for use. The acidic nature of vinegar can strip away the seasoning (the layer of polymerized oil that provides the non-stick surface) on the cast iron, leaving it vulnerable to rust and corrosion.
If the outer part of your cast iron pan is releasing black/silver residue when run under water, it could indicate that the pan has started to rust or that the seasoning has been compromised. Rust can affect the integrity of the pan and may render it unsafe for cooking.
To assess the condition of your cast iron pan, I recommend the following steps:
Thoroughly clean the pan: Wash the pan with warm water and mild dish soap to remove any remaining vinegar residue. Scrub gently with a non-abrasive brush or sponge. Avoid using harsh scrubbers or abrasive cleaners as they can further damage the pan's surface.
Inspect the pan: Carefully examine the pan for any signs of rust or pitting. If you notice significant rust or deep corrosion, it may be best to discontinue use as it can affect the pan's safety and cooking performance.
Re-season the pan: If the pan appears to be in decent condition with minor rust spots, you can attempt to re-season it. To do this, dry the pan completely and apply a thin layer of vegetable oil or shortening to the cooking surface, both inside and out. Place the pan upside down in an oven preheated to around 375°F (190°C) and bake it for about an hour. This process will help restore the protective seasoning layer.
After re-seasoning, monitor the pan closely during subsequent uses. If you notice any unusual flavors, odors, or ongoing issues with the pan's surface, it may be safer to replace it.
Remember, it's important to properly care for and maintain cast iron pans to ensure their longevity and safe use. Avoid prolonged exposure to acidic substances and always dry the pan thoroughly after cleaning to prevent rusting.