Investors who picked up Tianqi Lithium shares in Hong Kong’s biggest initial public offering (IPO) this year are expected to see the company’s stock decline in its trading debut, judging by prices indicated in pre-market trading. The stock is expected to fetch about HK$75.50 when trading begins on Wednesday, based on grey-market prices at local brokerages on Tuesday. That represents a 7.9 per cent drop from its HK$82 offer price. Tianqi Lithium will trade under the 9696 ticker. Investors may rue the timing of the IPO, as Chinese stocks in Hong Kong and mainland China suffered a knock just as…