Vinegar causes slow corrosion of iron by reacting with iron to form iron acetate and iron oxides, gradually degrading the nail over several days.1 day - The vinegar (acetic acid) starts reacting with the iron surface. You may see some bubbles (hydrogen gas) and a slight dulling or roughening of the nail’s surface as the acid begins to remove rust or oxidized layer.2 days - The reaction continues. The nail may start to develop a thin layer of iron acetate or slight corrosion. The surface might look more uneven or flaky.3 days - More noticeable corrosion appears. The nail may become weaker as the acid breaks down the metal, and the surface could show rust or reddish-brown patches due to iron oxide formation.4 days - The corrosion deepens. The nail may look rough, flaky, and rustier. The vinegar’s acid is eating through the metal, causing more surface damage.5 days - Significant corrosion is visible. The nail may be quite rusty, weakened, and possibly brittle. The acid might have eaten through some parts, making the nail fragile.