Steven Conway died while working at Diamond Wheels (Dundee) Ltd, a firm owned and operated by former Dundee FC director of football Paul Marr.
The 33-year-old was sent in to remove debris from a chemical tank with limited protective clothing in August 2011.
The firm will be sentenced for health and safety breaches in October.
Dundee Sheriff Court heard that Mr Conway sent into the tank containing "volatile" chemicals while wearing only trainers, tracksuit bottoms and a t-shirt and fleece.
The mask he was given did nothing to protect him from the toxic fumes let off by the chemicals, which were used to strip alloy wheels for cars.
Co-workers found the father of two unconscious inside the tank, and he was taken to hospital before being pronounced dead.
A post-mortem examination found he had suffered chemical burns from contact with hydrofluoric acid. Pathologists concluded he had died from inhaling industrial paint stripper.
Prosecutors said the tank Mr Conway was working in was not properly ventilated, the gloves he was given had holes in them and the face mask he was wearing was actually releasing "contaminants" into his air supply.
The court also heard that there were no safety protocols in place at the premises, no risk assessment was carried out and there was no safe system of work in place.
Defence advocate Gavin Anderson said the company had undertaken extensive efforts to adhere to health and safety standards since Mr Conway's death.
He said: "I express publicly in open court that Mr Conway's tragic death is genuinely and deeply regretted by all associated with the company.
"He had been a friend of Mr Marr for seven years prior to this and was valued not only as an employee but also as a friend."
Diamond Wheels (Dundee) Ltd, registered at Nethergate, Dundee, pleaded guilty to a charge under the Health and Safety at Work Act.
Sheriff Alistair Brown deferred sentence until October for the Crown and defence to make written submissions.
Addressing Mr Conway's parents in the public benches, he said: "Nothing that I can say or do will bring him back and I recognise that.
"It is certainly not the case in selecting a fine that I will be in any way seeking to put any kind of value on him or his life.
"It is important to keep in mind that Mr Conway died as a result of this - he's not to be forgotten in this process."
A Dundee company has admitted health and safety failings after a worker died while cleaning out a chemical tank.