Metal Finishing Guide Book

2013

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plating processes, procedures & solutions ANODIZING WITH ONE UNIVERSAL ELECTROLYTE USING PULSE-STEP-RAMP AND RUN PROCEDURES—A GREEN CHANGE FOR PROBLEM-SOLVING SITUATIONS BY FRED CHARLES SCHAEDEL, ANODIC TECHNICAL SERVICES, AFFILIATE OF ALPHA PROCESS SYSTEMS, WESTMINSTER, CALIF. Over the years, numerous problem-solving situations and major environmental considerations have necessitated the development of chrome-free mixed electrolytes. When used in conjunction with modified pulse – step – ramp procedures, these mixed electrolytes (organic sulfuric) are able to meet more demanding Type IC, II and III anodize requirements, and are very important in these major areas: QUALITY, EFFICIENCY, ENERGY SAVINGS PLUS ENVIRONMENTAL AWARENESS There are some concentrated additives and/or modifiers available along with specific organic acids which improve the sulfuric acid electrolyte. Many facilities are now using mixed electrolytes and/or stronger additives because in production problem-solving situations their performance characteristics are far superior to conventional sulfuric acid only baths. Problem-solving improvements were realized in smut prevention along with increased wear resistance and hardness, even in thinner films. They can also be used in the same Type II-III anodize tank over broad concentration and temperature ranges. This was the reason for the well-known MAE (Multi-Purpose Anodize Electrolyte) Process developed by Reynolds Metals during the 1960's in the performance of work done under a NASA contract (final patent Issued 1970)1. The MAE process also became the basis for most of the additives being marketed today, with the exception of those dependent upon coal tar and/or wood products including lignin wood sulfonates. Highly concentrated versions of the MAE process were developed representing major breakthroughs and are being used with sulfuric acid as one universal electrolyte for type II and III anodize. Pore structure developments from these concentrated carboxylic acid additives and modifiers contributed to major improvements in micro finish, color anodize and hardness for type III anodic coatings. Several patent applications made in 1962-68-69,79, 89 and 2003 refer to these improvements.2 Research, developments and improvements made for the universal electrolyte as presented here started in 1960, prompted by problem-solving situations. These problem-solving situations centered around three areas: Chemistry Power Supply Electronics Procedures : Sulfuric Organic Mixed Electrolytes : Slow and Fast Pulse (For difficult alloys _ 2024, 2219, 7050) : Pulse-Step-Ramp and Run Methodology The first problem-solving modifications to the electrolyte were (and still are) based on endothermic polycarboxylic complex ion chemistry. Later, numerous 223

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