Process for producing corrosion-resistant aluminum-coated iron surfaces

Claim 1

A PROCESS FOR PRODUCING CORROSION-RESISTANT ALUMINUM-COATED IRON BODIES, COMPRISING THE STEMPS OF DEPOSITING ON AN IRON BODY A SURFACE LAYER OF ALUMINUM OF A THICKNESS BETWEEN SUBSTANTIALLY 0.1 TO 0.4 MM., SUBJECTING SAID LAYER TO HEAT TREATMENT IN AN OXIDIZING ATMOSPHERE AT A TEMPERATURE BETWEEN SUBSTANTIALLY 690* AND 800*C. FOR A PERIOD SUFFICIENT TO CHANGE THE COLOR OF SAID SURFACE LAYER TO A SHADE OF GREY CHARACTERIZED BY A PHOTOMETRIC DENSITY VALUE BETWEEN SUBSTANTIALLY 0.1 AND 1.2 IN THE COLD STATE OF SAID LAYER UPON TREATMENT THEREOF BY LIQUID PARAFFIN, SAID PHOTOMETRIC DENSITY VALUE BEING THE LOGARITHM OF THE RATIO OF THE INTENSITY OF ILLUMILNATION INCIDENT UPON SAID LAYER TO THAT OF THE ILLUMILNATION REFLECTED BY IT, THEREBY RENDERING SAID SURFACE LAYER POROUS WHILE SIMULTANEOUSLY FORMING A DIFFUSE ALUMINUM-RION INTERFACE AT THE JUNCTION OF SAID LAYER WITH SAID BODY; SAID TREATMENT BY LIQUID PARAFFIN INCLUDING THE STEPS OF COOLING SAID LAYER TO A TEMPERATURE BELOW 400*C. AND IMMERSING IT IN A BATH OF SAID PARAFFIN HEATED TO A TEMPERATURE ABOVE ITS MELTING POINT WHEREBY SAID PARAFFIN PENETRATES INTO SAID LAYER, AND SUBJECTING THE PARAFFIN -TREATED LAYER TO A FURTHER HEAT TREATMENT AT A TEMPERATURE HIGHER THAN THAT OF SAID BATH AND BELOW 160*C.