It is the same with military vehicles. Yes, they get filthy, and in times of intense combat, they get battered and chipped etc, but once there is a lull in the fighting, the crews were expected to maintain and look after their charges. My friend Norman said that the designated driver or commander of the vehicle (British army, I am not so sure about other nations) could be put on a charge if the vehicle was rusty or in any other way unusable for duty not caused by enemy action. So, I don't doubt that the decks of those coal barges were scrubbed clean after loading and unloading.