Abdullah Ali of Ali's Convenience Store in Newport, Gwent, had ammonia sprayed in his face and was stabbed in the leg with a screwdriver when he tackled the assailant.
The robber fled the store empty-handed, but was traced through a mobile phone he left at the scene.
The thief, who cannot be named for legal reasons, was sentenced to 18 months in a detention centre after pleading guilty to robbery, attempted robbery and unlawful wounding.
Abdullah said the sentence did not match the severity of the crime. "I don't think it's a deterrent at all. It's an indication that crime pays, not even a slap on the wrist.
"In 18 months, he would have forgotten about it, whereas I've got to live with this incident for the rest of my life."
It was revealed that the perpetrator had also robbed the nearby Lifestyle Stores and attacked store worker Ali Riaz with a knife.
Neither retailer suffered lasting injuries, but Ali has since quit his job at the store.
In a submission to a recent consultation on sentencing guidelines for assault, the Association of Convenience Stores called for sentences for attacks against shop workers to equal those of public service workers such as police officers and ambulance drivers.
The family of murdered Huddersfield retailer Gurmail Singh have also launched a petition calling for harsher sentencing for crimes against retailers. They hope to present the petition to Downing Street in the coming weeks.