Is there a way to get the pdf's without need to pay?
Even old standards would be fine. I know there is this russian site that has them in russian, but it's very incomplete, they have like the 1% of them and they need manual translation.

Are there websites offering leaked pdf's of ISO standards for free?

I specifically need this one: ISO 6178-1983:

Centrifuges — Construction and safety rules — Method for the calculation of the tangential stress in the shell of a cylindrical centrifuge rotor

Thanks bros