The shares of Alcoa Corp (NYSE:AA) are sliding today, after news that the company is aiming to buy Alumina for $2.2 billion in an all-stock deal. Dropping aluminum prices are denting Alumina, and the merger would provide tax advantages to both. At last glance, AA was down 2.9% at $25.75, earlier as low as $24.86 -- its lowest level since mid December. The stock is below all moving averages between the 20-day and 320-day, with recent pressure from the former. Since last February, the equity is down 44.8%. Op ...