Impairment tests required by international accounting rules undercut second-quarter results at Brazilian long-steel maker Gerdau SA (GGB), which plummeted because of non-recurring charges, the company's chief financial officer said Thursday.

Gerdau reported a second-quarter net loss of 329 million Brazilian reals ($181 million), down from a net profit of BRL2.12 billion in the same quarter a year ago. During the quarter, Gerdau posted a non-recurring charge of BRL1.08 billion, the company said.

"It's very important to understand that 90% of the charge has no impact on cash flow," CFO Osvaldo Schirmer said during a conference call.

Gerdau was forced to take the write-downs for idled steel capacity, intangible assets and goodwill under impairment tests required by International Financial Reporting Standards, Schirmer said.

The tests reconcile the present value of assets with future estimated earnings and book values, the executive said.

Gerdau idled several blast furnaces and reduced production capacity amid the broader economic slowdown. It also had to recognize goodwill amortizations for a flurry of acquisitions made in recent years.

The charges should be reverted as capacity is brought back online, a process that is under way on signals that demand is returning, Schirmer said.

Gerdau plans to keep several blast furnaces in the U.S. operating - they had previously been expected to be shut down. In Brazil, the No. 2 blast furnace at Acominas will be kept hot after the company shelved plans to shut it down for maintenance.

"In general, steel operations are working at about 60% to 70% of capacity," Gerdau Chief Executive Andre Gerdau Johannpeter said.

-By Jeff Fick, Dow Jones Newswires; 55-21-2586-6085; Jeff.Fick@dowjones.com