Reuters reported that China's full trade report for May sprung few surprises in terms of headline imports of base metals.

As flagged by the preliminary snapshot released earlier this month net imports of refined copper were weak at 129,000 tonnes, albeit slightly higher than those in April thanks to a drop off in exports to 20,000 tonnes from 44,500 tonnes.

Net imports of primary aluminium shrank to 3,300 tonnes the lowest monthly figure so far this year while exports of product accelerated to a new all time high of 340,000 tonnes. The latter is thought to reflect exporters rushing to beat an expected tightening of the tax rebates on several product categories.

Net imports of both tin and nickel at 800 tonnes and 13,600 tonnes respectively marked a continuation of recent trends. Net trade in lead remains broadly flat, while China continues to import zinc it doesn't need in what appears largely a function of financial arbitrage.

More interesting this time around were some of the raw materials numbers. NICKEL ORE SURGE China's imports of nickel ore and concentrates surged to an all time high of 4.19 million tonnes far eclipsing the previous high of 2.85 million tonnes in September 2009. Booming imports, in excess of 2 million tonnes from both Indonesia and the Philippines were the driver.

Ore imports from these two countries feed nickel pig iron producers and as such are a widely used proxy for what is happening in the NPI sector which doesn't make it onto the official count of Chinese nickel production. It's an imperfect proxy. For example, it is quite possible that May's super high figure reflects stock building rather than actual NPI production.

Yet the broader trend is one of steadily rising ore imports. They jumped by 52 percent last year and are already up by another 62% this year. That would seem to back up anecdotal evidence that NPI production is on a surge in China, reflecting a new generation of operators that are increasingly integrated with stainless steel mills.

China's imports of alumina, by contrast, slumped to a multi year low of 113,500 tonnes in May. It wasn't a rogue figure. Imports fell by 16 percent last year and have fallen harder still this year. The cumulative January and May total of 945,000 tonnes marked 57% YoY drop.

Remember that Chinese aluminum smelters have been churning out record amounts of the light metal this year so the slump in alumina imports is not for want of demand. Rather, China's own alumina production has been rocketing in recent months. It surpassed the 3 million tonne level for the first time ever in May and cumulative output this year has increased by 16%.

Indeed, based on figures from the National Bureau of Statistics and using a 2:1 ratio for the amount of alumina needed to make one tonne of aluminum, China has been generating a surplus of the raw material for the first time ever this year. Not that it is self sufficient in the bauxite needed to make the alumina. Imports hit a new high of 4.5 million tonnes in May and cumulative flows jumped by 56 percent in the first five months of 2011.

China's imports of copper raw materials have been less clear cut so far this year. Imports of scrap were up by 6% YoY in the first 5 months. They have been running at a very steady monthly rate of close to 400,000 tonnes for some time now.