Quick google, they were galvanised!
The Porsche 944 was galvanised at the factory. This is a simple coating to the bodywork which inhibits rust formation. In reality this system has worked very well, but now, some three decades after the launch of the car, the evil rust is beginning to become a problem on some examples, so is something to look out for. In particular rust tends to form in the following locations:
rear of sills on the outside. Often seen as bubbling of the stone chip textured paint coating;
Rear of sills on the inside. Check between the inner sill and the rear suspension beam for a hole forming about 6 inches in front of the rear wheel arch on the inside, easily reached by holding the bottom of the sill and probing with your fingers;
Front wing bottoms. The lower trailing edge of the wheel arch accumulates a lot of road debris, which then causes the bottom of the wings to corrode. Look for blisters, orange staining and probe this area. If it makes a crunching noise, it needs repairing. New front wings are expensive, however a good bodyshop can rebuild this area in steel;
Front wings where they meet the front bumper. Not often serious or holed, but it is becoming more common to see some rust blisters forming in this area;
Between back bumper and back panel right bellow the Porsche script decal. I believe that for some reason insufficient paint was applied by the factory in this area, as the inside edge from the luggage area always seems to be fine, but often blisters can be seen between the bumper and the back panel. These are normally superficial;
Around the windscreen, again usually superficial, but for some reason it seems occasionally the 944 can blister around the windscreen trim.