He will also read out a message from the President of the Seafarers charity, HRH The Earl of Wessex, once the flag has been raised.
The ceremony will be observed across the UK on Merchant Navy Day as well as formally observed in Canada, Australia and New Zealand.
Merchant Navy Day has been commemorated since 2000 on September 3, the anniversary of the sinking of the SS Athenia, the first British merchant vessel lost during the Second World War.
Cllr Black said: “As the son of a merchant seaman it will be an honour for me to raise the Red Ensign flag outside the Town Hall in recognition of the courage and sacrifice of these often unsung heroes.
“The Merchant Navy was brave and courageous during the war when every voyage must have been extremely dangerous and difficult. And today they play such a vital role.”
As an ‘island nation’ the UK relies on Merchant Navy seafarers for 95% of our imports, including half the food we eat. The UK has the largest ports industry in Europe.
Around 75% of our exports - by volume - are shipped from UK ports, some of which are supporting the campaign by encouraging visiting ships to sound their horns at 10am on September 3.