Of those tanks only one sits on China's boarders. People keep pointing to K2 but here are two reality checks.China is in a unique situation where despite having the MOST number of neighoring nations (14 nations, tied with Russia), it really only has two potential enemies - Russian T-90S and Korean K2 Panther.
1) it's K2 and K1A2. The South Koreans have both tanks and are not yet showing evidence of retiring the latter. Infact they continue to modernize.
2) however between The PRC and ROK is the DPRK. Who maintains a huge number of tanks of there own.
Tanks that are at last check not to the spec of the current K2 or T90S but still a potential trouble.
South Korea is not at war with China if anything they seem to be a neutral power vs the Chinese intent on not being beholden but also not directly interfering. The only issue the PRC really has with the ROK is it's a US Allie.
Their interest is the DPRK.