What benefit do tie coats provide in a multicoat system?

Tie coats play a crucial role in multicoat painting systems primarily by improving adhesion between layers. When applying multiple coats of paint, it's essential that each layer adheres properly to the layer beneath it to ensure the longevity and effectiveness of the entire paint job. Without appropriate adhesion, layers can separate or peel over time, which can lead to premature failure of the finish.

Tie coats are specifically formulated to create a suitable surface for the subsequent layers, often acting as a bonding agent that enhances the intercoat adhesion. This is particularly valuable when transitioning from one type of coating to another, such as when applying a water-based paint over an oil-based paint, where adhesion issues might otherwise arise.

While the other options suggest potential effects of tie coats, they do not accurately capture the primary function as effectively as the correct answer does. Tie coats may affect drying time or overall durability indirectly by their function, but their main purpose remains focused on ensuring that each layer bonds appropriately to create a strong, cohesive finish. Changing the color of a paint system is typically a separate consideration that does not relate to the purpose of a tie coat.