In 1920, he was elected to the works committee of his mine, and from 1929 he was the full-time union official for Bochum and Castrop-Rauxel.
He set up his own business, then during World War II was conscripted into the air raid police.
After the war, he was immediately elected as town clerk of Castrop-Rauxel, and joined the new IG Bergbau union.
In 1953, the position of president of IG Bergbau became available and, although Heinrich Gutermuth won, he immediately stood down in favour of Imig.
The following year, Imig was also elected as president of the Miners' International Federation.