아래 사이트에 수산법, 황산법, 크롬산법을 간단하게 잘 정리하셨네요. http://m.blog.daum.net/dongguk2092/25 크롬산법을 적용하지 않는 이유를 아래와 같이 설명합니다. "일본에서는 직교류 중첩을 이용한 수산법이 주종이고 우리나라 및 구미에서는 황산법을 이용하여 직류만을 사용하는 방법이 80%이상 차지한다. 크롬산법은 공해 및 건강상의 문제로 연구소 쪽에서만 가끔 행해진다."

아주 약식으로 비교해 봅니다. The two most common processes are Chromic Acid (Type I) anodizing and Sulfuric Acid (Type II and Type III) anodizing. Type I is used for thin coatings (0.00002” to 0.00007” or 0.5μ-7.6μ), typically to provide chemical resistance. Since chromic acid by itself does not attack Aluminum, post-anodizing cleaning and rinsing is not as critical as with other processes. It is greatly limited to use due to carcinogen risk of chromium VI, however it is still used for military and aerospace products, or specific application required by purchaser (or end-user). Type II, is used as “standard anodizing”, results in a thicker layer (0.00007”-0.0001” or 1.8μ-25.4μ) and is used to prepare parts to be dyed and to increase wear and scratch resistance and lubricity. Type III, also known as “hard anodizing”, leaves an even thicker layer (0.0005”-0.006” or 12.7μ-115μ) and is used to further increase wear and corrosion resistance, and thermal and electrical insulation. Thicker oxide layers require stricter process controls, often requiring refrigerated acid-baths and carefully timed voltage cycles. 더욱 자세한 내용은 앞선 답글과 ASM Metal HB vol.5, Surface Engineering, Section for Anodizing 이나 Internet을 통해 찾아보실 수 있을 겁니다. 특히, “chromic acid anodizing carcinogen” 으로 검색을 하시면 금지 또는 제한 규정들을 찾아 볼 수 있을 겁니다. Thomas Eun