Sales of corporate bonds globally surged to the most on record for August as issuers rushed to lock in record-low borrowing costs.

Siemens AG, Europe's largest engineering company, and JPMorgan Chase & Co. led borrowers selling $237.6 billion of debt this month, exceeding the $235.3 billion raised in August 2010, according to data compiled by Bloomberg. Yields fell to an unprecedented low of 3.72 percent on Aug. 28, according to Bank of America Merrill Lynch index data.

Offerings are increasing as issuers take advantage of demand with default rates below historic averages and optimism rising that Europe's leaders may contain the region's fiscal strains. While yields on corporate bonds average less than 4 percent, the spread to U.S. Treasuries is higher than before the credit crisis. Government bond yields have been suppressed by central banks easing monetary policy to stimulate growth.