Portuguese to English Tech/Engineering Fisheries engines

Hi - this is in a transcript, a fisherman explaining how zincs work on the boat. I understand the concept of zincs - I'm just not sure how to express this particular idea in English. The idea is to be faithful to the way he is speaking and describing the process. Could it possibly be translated as 'it's for the current from the engine'? The idea of 'diffusion' from an engine doesn't sound right to me... Country is Portugal.

ZINCOS
— Mas aí os zincos que vocês estavam a falar, isso serve para quê?
— Por causa da difusão do motor ao trabalhar, para não comer a ferragem e o metal do… ferro, do ferro, do barco.

Thanks in advance.