Joints shall be brazed within _______ hours after the surfaces are cleaned for brazing.

• A. One
• B. Eight
• C. Twenty-four
• D. Four

Answer: (B)

After cleaning, brazing must be completed within eight hours. The reason is that clean metal surfaces quickly begin to oxidize again when exposed to air. Oxidation and surface contaminants interfere with the flux and the capillary action needed for the filler metal to wet and fill the joint properly. Keeping the brazing within this eight-hour window helps ensure a sound, leak-free joint without needing re-cleaning. If more time passes, you’d typically re-clean and re-flux to restore proper surface conditions before brazing.