# US 4,394,184 A · Determination of grain refiners in phosphate conversion coating baths > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 4,394,184 A - Document ID: US4394184A - Status: Granted - Kind: A - Application number: 06/362,572 - Filed: 1982-03-26 - Granted: 1983-07-19 - Earliest claimed: 1982-03-26 - Assignees: Pennwalt Corporation - Inventors: Richard G. Adams - Web page: https://patentgrep.com/patent/US4394184A ## CPC - C23C 22/08: Orthophosphates - Y10T 436/12: Condition responsive control - Y10T 436/16: Phosphorus containing - Y10T 436/163333: Organic [e.g., chemical warfare agents, insecticides, etc.] - C23C: COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL (making metal-coated products by extrusion B21C23/22; covering with metal by connecting pre-existing layers to articles, see the relevant places, e.g. B21D39/00, B23K; metallising of glass C03C; metallising mortars, concrete, artificial stone, ceramics or natural stone C04B41/00; enamelling of, or applying a vitreous layer to, metals C23D; treating metal surfaces or coating of metals by electrolysis or electrophoresis C25D; single-crystal film growth C30B; by metallising textiles D06M11/83; decorating textiles by locally metallising D06Q1/04) - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## Abstract The amount of organic, phosphorous containing grain refiners in phosphate conversion coating baths is determined by precipitating the grain refiners and determining the difference in the chemical oxygen demand of the bath before and after the precipitation. ## Claims ### Claim 1 A process for determining the concentration of a phosphorous containing organic grain refiner in an aqueous, acidic conversion coating bath which includes an inorganic divalent metal phosphate comprising, determining the chemical oxygen demand of the bath, precipitating the grain refiner from a portion of the bath by raising the pH to above about 4.0 in the presence of excess metal ion, determining the chemical oxygen demand of the precipitated portion of the bath, and determining the concentration of grain refiner in the bath from the difference between the chemical oxygen demand of the bath and the precipitated portion of the bath. ### Claim 2 (depends on 1) The process of claim 1 wherein the grain refiner is precipitated by adding a base to raise the pH to at least about 4.0 in the presence of a metal ion which forms an insoluble salt with the organic phosphorous compound. ### Claim 3 (depends on 2) The process of claim 2 wherein the grain refiner is precipitated by raising the pH to at least about 6.5. ### Claim 4 (depends on 3) The process of claim 3 wherein the metal ion is selected from the group consisting of zinc, nickel, magnesium, calcium, manganese, bismuth, lead and mixtures thereof. ### Claim 5 (depends on 1) The process of claim 1 wherein the phosphate is zinc phosphate. ### Claim 6 (depends on 5) The process of claim 5 wherein the grain refiner is selected from the group consisting of acidic organic phosphates and phosphonates having at least one free hydroxyl group. ### Claim 7 (depends on 6) The process of claim 6 wherein the grain refiner is 1-hydroxyethylidene-1,1-diphosphonic acid. ### Claim 8 In a process for forming a metal phosphate conversion coating on a metal surface which comprises contacting the metal surface with a heated, acidic, aqueous bath which includes a divalent metal phosphate, an oxidizing accelerator and a grain refiner selected from the group consisting of acidic organic phosphates and phosphonates having at least one free hydroxyl group, the improvement comprising monitoring the amount of grain refiner in the bath by periodically determining the chemical oxygen demand of the bath, precipitating the grain refiner from a portion of the bath by raising the pH to above about 4.0 in the presence of excess metal ion, determining the chemical oxygen demand of the precipitated portion of the bath, determining the concentration of grain refiner in the bath from the difference between the chemical oxygen demand of the bath and the precipitated bath sample and adjusting the amount of grain refiner in the bath to bring it to a desired concentration. ### Claim 9 (depends on 8) The process of claim 8 wherein the grain refiner is precipitated by adding a base to raise the pH to at least about 4.0 in the presence of a metal ion which forms an insoluble salt with the organic phosphorous compound. ### Claim 10 (depends on 9) The process of claim 9 wherein the grain refiner is precipitated by raising the pH to at least about 6.5. ### Claim 11 (depends on 10) The process of claim 10 wherein the metal ion is selected from the group consisting of zinc, nickel, magnesium, calcium, manganese, bismuth, lead and mixtures thereof. ### Claim 12 (depends on 8) The process of claim 8 wherein the phosphate is zinc phosphate. ### Claim 13 (depends on 12) The process of claim 12 wherein the grain refiner is selected from the group consisting of acidic organic phosphates and phosphonates having at least one free hydroxyl group. ### Claim 14 (depends on 13) The process of claim 13 wherein the grain refiner is 1-hydroxyethylidene-1,1-diphosphonic acid.