Phosphate coating composition and process

Claim 1

A LIQUID COMPOSITION FOR THE PRODUCTION OF PHOSPHATE COATINGS ON FERROUS SURFACE, SAID COMPOSITION CONSISTING OF AN AQUEOUS SOLUTION COMPOSED OF AT LEAST ONE SUBSTANCE SELECTED FROM THE GROUP CONSISTING OF PHOSPHORIC ACID, AMMONIUM PHOSPHATE AND THE ALKALI METAL PHOSPHATES, SAID PHOSPHATE BEING PRESENT IN A CONCENTRATION OF FROM 0.05 MOLAR AND AT LEAST ONE REDUCIBLE COMPOUND SELECTED FROM THE GROUP CONSISTING OF M-NITROBENZENE-SULPHONIC ACID IN AN AMOUNT OF .05 PERCENT TO .25 PERCENT, O-NITROCHLORBENZENE-P-SULPHONIC ACID IN AN AMOUNT OF .5 PERCENT TO 2 PERCENT, 3-NITROPHTHALIC ACID IN AN AMOUNT OF .02 PERCENT TO 1. PERCENT, M-NITROBENZOIC ACID IN AN AMOUNT OF .02 PERCENT TO .1 PERCENT, AND THE SALTS THEREOF IN A CONCENTRATION EQUIVALENT TO THE CONCENTRATION OF THE CORRESPONDING ACID, SAID SOLUTION CONTAINING SUFFICIENT ALKALINE MATERIAL TO PRODUCE A PH WITHIN THE RANGE OF 4.2 TO 5.8.