46 CFR §56.75-25

1. (a)Pipe may be fabricated by brazing when the temperature to which such connections may be subjected does not exceed 425 °F. (For exception refer to § 56.30-30(b)(1).)
2. (b)The surfaces to be brazed must be clean and free from grease, oxides, paint, scale, and dirt of any kind.
3. (c)After the parts to be joined have been thoroughly cleaned the edges to be brazed must be given an even coating of flux prior to heating the joint as a protection against oxidation.