Whitewashing once meant:
painting a wall with a white paint made of slaked lime and chalk, which reacted after applying to the wall with carbon dioxide in the atmosphere to form calcium carbonate in the form of calcite. Calcite has a beautiful white colour and is very resistant to weathering after hardening, a chemical process called curing.
In this sense the term was first used in 1591, according to my Merriam-Webster. And that is easy to translate into Spanish as encalar or into German as kalken.
But the other, more relevant meaning in modern times refers to the practice of
a: to gloss over or coverup (as vices or scandals);
b: to exonerate by means of a perfunctory investigation or through biased presentation of data (again according to Merriam-Webster).
This is related to the German concept of Persilschein, but not an exact match. I would say that a Persilschein can be granted after an exercise in whitewashing or as a result thereof, but causation does not mean identity.
In the case of the Spanish language the problem is even more protracted, as Spanish doesn’t even know the concept of Persilschein, let alone whitewashing in the meaning we are discussing. The same is true for the related concept of greenwashing, which could be defined as a variety of whitewashing that strives to give green credentials where none are due. Spanish doesn’t know this concept either. Just like spin-doctoring it seems to be a concept difficult to grasp in Spanish, which is quite astonishing, given the chutzpah and the nonchalance with which it is actually done. Why might this be? Or is it just a figment of my imagination?