UltraFlux Black


UltraFlux Black is a boron modified, water based active fluoride/borate-type flux in paste form. It is formulated to ensure a creamy consistency and to provide excellent adhesion when dipped or brushed on components. UltraFlux Black is best used with filler metals that flow between 1050°F (566°C) - 1800°F (982°C). The flux provides excellent protection of components up to 1800°F (982°C).


UltraFlux Black is general purpose brazing flux primarily used in applications involving brazing of steel, stainless steel, copper, copper alloys, nickel, and nickel alloys. It is not recommended for use in aluminum bronze or other aluminum alloy brazing applications. UltraFlux Black is suitable for use with most heating methods including torch, furnace or induction. This product exhibits excellent adhesion, oxide absorbing capabilities, and minimal splattering during the brazing process. Flux may require mixing, dilution or warming to regain its normal consistency prior to use.


This product is corrosive, and post-braze cleaning or rinsing is required. The flux residue is easily dissolved in hot water at temperatures of 120°F (50°C) or higher.


If stored for an extended period of time some separation within the flux may occur. In such case stir the flux until proper consistency is restored. UltraFlux Black readily dilutes to slurry consistency (per AWS A5.31M/A5.31 Specification for Fluxes for Brazing and Braze Welding) using 60cc of cold or hot water per pound of flux. Care must be exercised when adding water as the concentration of fluxing salts is reduced and spitting may increase. Water concentration of original product is 35% by weight of flux.

UltraFlux Black is warranted for twelve months from the date of shipment if stored in the original, unopened container. Optimal storage condition is dry, cool ambient temperature 65°F (18°C) - 75°F (24°C). Twelve months should not be interpreted as the shelf or useful life of the product unless actual test results indicate unsatisfactory performance for the intended application. Flux stored beyond the warranty period may be reconstituted to a working consistency by warming in a water bath and/or by adding distilled or de-ionized warm water.

Flux, when placed on a U.S. standard 40 mesh (425 micron) sieve conforming to ASTM E11 and worked lightly with a brush shall pass completely through the sieve. If the flux has coagulated partially in the container, prior to testing, the flux may be warmed in a water bath until it has returned to its normal consistency.


  • American Welding Society (AWS) A5.31 FB3C
  • Society of Automotive Engineers (SAE) / AMS 3411
  • Federal Specifications O-F-499D, Type B


UltraFlux is available in a number of packaging options including: ½ lb, 1 lb, 5 lb, 25 lb and 50 lb containers.


  Boron modified Temp Range °F Temp Range °C AWS A5.31 SAE/AMS
UltraFlux No 1100 - 1600 593 - 871 FB3A 3410
UltraFlux Black Yes 1050 - 1800 566 - 982 FB3C 3411



The operation and maintenance of brazing equipment or facility should conform to the provisions of the American National Standard (ANSI) Z49.1, Safety in Welding and Cutting. Refer to the Safety Data Sheet for more information.