Carole Hodson was managing director of Wednesbury-based Alca, which made nuts and bolts for the oil, gas and construction industries, when she was approached by Terje Moe, known as a "kingpin" in the Norwegian oil industry.
The 63-year-old from Wolverhampton, paid him almost £300,000 over five years, creating false invoices to disguise the secret payments, it was said. Moe was known in the office as "you know who", the court heard.
A system of monthly payments was set up, paid directly into his personal bank account, in return for orders from his employers, The Wurth Company, said Miss Rachel Barnes, prosecuting.
Hodson had taken over a controlling interest of Alca, on the Darlaston Central Trading Estate, a few years earlier in 2000, and saw turnover soar following the slush fund arrangement with Moe, enjoying a lifestyle to match, the court heard.
On one occasion, Hodson sent bespoke jewellery to Moe in a Jiffy bag placed within a shipment to his employer.
But the racket came to an end in July 2016 with Hodson claiming she stopped voluntarily because Moe, who had asked for more money, was "getting too greedy", the court heard.
She also told investigators that she realised "the payments were wrong and they had to stop".
However Moe had ceased acting as his company's buyer two months earlier when he went on sick leave, Wolverhampton Crown Court heard.
Hodson, who talked to him four or five times a day, would have known he was ill, making her claim that the ending of the payments was voluntary "simply not credible", said the judge.
The defendant, of Birchfield Avenue, Tettenhall, pleaded guilty to bribery between July 2011 and July 2016 totalling £293,234 over 64 payments, and was sentenced on that basis, but the prosecution claim the offending covered a much longer period, with bribes amounting to more than £500,000 in all.
Moe was arrested in Norway and admitted accepting bribes from Hodson between 2007–16. He was jailed for two years and eight months.
To maintain the value of her company prior to selling it for £15.5m in 2017, Hodson lied to the new owners by claiming it had not been involved in any unlawful conduct, it was said. The court heard its true value had since plummeted.
Mr Andrew Smith, QC, defending, argued Hodson had not initiated the bribes and had been motivated to continue by fear of losing the business and jeopardising the jobs of her 20 employees. She was of previous good character and considered a "business leader".
Passing sentence, Judge Amjad Nawaz described the offence as "deliberate, calculated and sophisticated", with "a "huge element of self-enrichment for her."
Her corrupt dealings had struck at the core of commercial life because she had deprived competitors of a level playing field. Such offending "has been likened to cancer because it erodes confidence," he added.
A confiscation order of £4.5m was made. Hodson was also ordered to pay the £478,350 prosecution costs and disqualified from holding office in a limited company for seven years. Two members of her office staff are also being investigated.