Hello
methods A, B, etc. in ASTM TM 0177 are related to the loading type : method B is the "bent beam" method that differs from "method A, tensile".
please have a look in the document you make reference to (NACE TM 0177)
regards
The B method was put in by Shell when I was on the committee in the 80's and 90's. At that time I don't recall any company but Shell using it routinely. At that time people who wrote the NACE documents got no compensation from NACE. NACE Staff did the editorial and publishing work.