The phrase "eat through" means to gradually erode or consume something over time. Its antonyms include phrases like "build up," "reinforce," and "strengthen." These phrases all suggest the opposite of erosion or consumption, implying that something is being made stronger or more resilient. In the context of digestion or corrosion, other antonyms might include "protect," "preserve," or "seal." These phrases all suggest protecting something from being eaten through or damaged. Overall, the antonyms for "eat through" serve to illustrate the opposite of something being slowly eroded over time, implying instead a process of strengthening or protecting.