Aluminum giant Alcoa (NYSE:AA) announced on Feb. 12 that it was selling its holdings of iron ore company Rio Tinto (NYSE:RTP)to Chinalco for about $1 billion, nearly $700 million more than the current value of the holdings. And speculation has begun to surface that Chinalco will make a play for Alcoa, one of the world's largest producers of aluminum.

MOST NOTEWORTHY: General Motors (GM), Aluminum Corp of China (ACH), Greenbrier Cos (GBX) and Monsanto (MON) were today's noteworthy downgrades:

• Bear Stearns cut General Motors (NYSE: GM) to Peer Perform from Outperform based on valuation and growing fundamental headwinds.

• HSBC downgraded Aluminum Corp of China (NYSE: ACH) to Underweight from Neutral as they believe prices of lightweight metal have peaked.

• Greenbrier Cos (NYSE: GBX) was cut at Bear Stearns to Peer Perform from Outperform on valuation.

• Matrix USA downgraded Monsanto (NYSE: MON) to Buy from Strong Buy on valuation...

OTHER DOWNGRADES:

• Sandler cut Western Alliance Bancorporation (NYSE: WAL) to Hold from Buy.

• UBS cut Arris Group (NASDAQ: ARRS) to Neutral from Buy.

• AG Edwards downgraded Hilton Hotels (NYSE: HLT) to Sell from Buy. Gabelli cut Hilton Hotels to Hold from Buy.
  

Analyst summaries provided by TheFlyOnTheWall.com (subscription required).

Alcoa Inc. (NYSE:AA) sets the stage for the fourth-quarter earnings season tomorrow. Analysts are expecting the No. 1 aluminum producer to report profit of 65 cents compared with 35 cents a year earlier, according to Thomson Financial. Expectations range from 53 cents to 72 cents. Revenue is seen at $7.63 billion, up 14 percent.

As MarketWatch points out, Alcoa is benefitting from soaring prices for aluminum, which as of December were $1.32 per pound, up 23 percent from a year earlier. Wall Street always looks to Alcoa as a barometer for the rest of the S&P 500 given the breadth of its customer base.

Alcoa posted disappointing third quarter results because of unplanned outages. Last month, a union representing 830 workers at the company's plant in Cleveland voted to end an eight-week strike.

Earnings for the S&P 500 are expected to rise 9.9 percent in the fourth quarter, down from 19 percent in the third, according to MarketWatch. "No doubt there is definitely an expectation for slower growth, but taken into the context of the long-term average for the S&P 500 (of 7.5%), it's more like we're getting back to the mean after a solid run for three years," said Thomson research analyst John Butters told MarketWatch.