How do you take away sweet taste on corn chowder?

In a canned clam chowder, you can't really reduce the saltiness. (You can dilute the chowder by one half by adding an extra can of milk, cream, roux, etc., but this affects flavor.)

The best way to achieve a less-salty clam chowder is to make your own. It's not hard--here's an easy one:

Make a roux with butter and a small amount of flour--a roux is easy to make, consult any cookbook--the roux thickens the soup

Slowly mix in 2 cups of whole milk and 1 cup of dry white wine or a light-colored beer, whisking until the soup is thick again before adding more

Add black pepper, nutmeg, the juice of one lemon, and salt to taste (or omit salt)

Dice three or four red or new potatoes

Simmer the diced potatoes in the chowder for 10 minutes until they are just tender

Add two cans of drained clams (more if you like) and a cup of drained canned corn

Simmer until heated through

Serve immediately, garnish the top with oyster crackers or diced scallions/green onions