Is it illegal to post license plates privately in industrial areas?

It's not illegal, but the property should not do this.

I suggest you take photos and video for evidence collection.

It is illegal for a motor vehicle driver to intentionally block the license plate, but it is not illegal for the vehicle to block the license plate in the community.

It is illegal to block the license plate when the vehicle is on the road.

Legal basis:

Article 90 of the Road Traffic Safety Law of the People's Republic of China, if a motor vehicle driver violates the provisions of laws and regulations on road traffic safety, he shall be given a warning or fined from 20 yuan to 200 yuan. If there are other provisions in this law, it shall be punished in accordance with its provisions.

Article 95 If a motor vehicle running on the road is not equipped with a motor vehicle number plate, inspection mark or insurance mark, or does not carry a driving license or driver's license with it, the traffic control department of the public security organ shall detain the motor vehicle, notify the parties concerned to provide the corresponding number plate or mark or go through the corresponding formalities, and may impose penalties in accordance with the provisions of Article 90 of this Law.

If the parties provide the corresponding number plate, logo or complete the corresponding procedures, they shall return the motor vehicle in time. Whoever intentionally conceals, defaces or fails to install the motor vehicle number plate in accordance with the provisions shall be punished in accordance with the provisions of Article 90 of this Law.