Heat exchanger with variable thickness coating

A heat exchanger comprising:

• an inlet face arranged to receive ram air;
• an exit face opposed from the inlet face;
• a plurality of heat exchanger walls extending between the inlet face and the exit face, the plurality of heat exchanger walls defining a plurality of passages that open at respective leading edges at the inlet face and at respective trailing edges at the exit face;
• and
• a coating lining the plurality of heat exchanger walls, the coating having a thickness that varies according to location on the plurality of heat exchanger walls.

A method of protecting a heat exchanger from corrosion, the method comprising:

• providing a heat exchanger wall that bounds a passage;
• identifying at least one location on the heat exchanger wall that is more susceptible to corrosion than at least one other location on the heat exchanger wall;
• and
• providing a coating on the heat exchanger wall in a thickness that varies according to the identified locations such that the coating has a first thickness T1 at the location on the heat exchanger wall that is more susceptible to corrosion and a second, different thickness T2 at the least one other location on the heat exchanger wall, where T1 is greater than T2.