DuraKapp™ #2 and #4X Babbitt

DuraKapp™ Babbitt alloys #2 and #4X are the most common alloys for wear coating moving parts in modern high pressure gas and air compressors. These Babbitt alloys offer an unsurpassed combination of compatibility, conformability, and embed ability. They easily adapt their shapes to conform to the parts and will hold a lubricant film. Foreign matter not carried away by the lubrication is embedded below the surface and rendered harmless. Even under severe operating conditions, where high loads, fatigue problems, or high temperature dictate the use of other stronger materials, DuraKapp™ #2 and #4X Babbitt are often employed as a thin surface coating to obtain the advantage of their good rubbing and lubrication characteristics.

More information can be found at DuraKapp™ #2 Babbitt and DuraKapp™ #4X Babbitt.

  Air & Gas compressor image

KappZapp™, KappFree™ and KappTec™ Solders in Compressor Switches,  Controllers and Sensors

KappZapp3.5™ and KappZapp4™ are the most common alloys used in soldering Copper wire and tabs in compressor switches, sensors and controllers. Whether in solid wire, rosin, or acid cored, strength, vibration resistance and electrical conductivity all go up with an increase in the Silver (Ag) content. The price also increases with the Silver Content. So the challenge is to choose the solder that meets your needs without buying more Silver than you need. Where strength and vibration resistance are not the primary criteria for your project, KappFree™ Tin-Copper-Silver solder is a more cost-effective Silver solder for most applications.


KappZapp3.5™ is the most convenient formulation, as it melts at the low eutectic temperature of 430°F / 221°C. For many hand soldering applications, KappZapp4™ is utilized for its wider slushy range of 430 - 475°F / 221 - 246°C.




96.5Sn - 3.5Ag


96Sn - 4Ag


93Sn - 7Ag



Solidus(°F) /(°C)

430°F / 221°C

430°F / 221°C

430°F / 221°C

440°F / 226°C

Liquidus(°F) /(°C)

430°F / 221°C

475°F / 246°C

570°F / 299°C

500°F / 260°C

Tensile Strength (copper)

14,000 psi

14,000 psi

15,500 psi

10,000 psi

Tensile Strength (stainless)

25,000 psi

28,000 psi

31,000 psi

18,000 psi

Shear Strength

11,600 psi

12,000 psi

14,000 psi

5,000 psi






Electrical Conductivity (%IACS)






KappFree™ solder was formulated specifically to provide the flow and bonding characteristics of higher Silver solders without buying more Silver than you need. It behaves similar to KappZapp™, meets NSF requirements as Lead-Free and Cadmium-Free, and actually has a higher electrical conductivity than KappZapp™ solders.


Finally, in high temperature environments, KappTec™ solder offers superior bonding, strength, vibration resistance, and electrical conductivity. See the chart below for key alloy characteristics.




Cd (Cadmium):


Ag (Silver):



Technical Data

Melting Range:

640-740°F (338-393°C)


.3153 lbs./in3. / 8.727g/ml

Electrical Conductivity:

22 (% IACS)

Electrical Resistivity:


Shear Strength (Copper):

11,000 psi @ 72°F (22°C)

Shear Strength (1020 Steel):

12,000 psi @ 72°F (22°C)

Tensile Strength:

Up to 25,000 psi

Specific Gravity:


*Shear strength based on double lap joints


NOTE: Cadmium is a health hazard. See SDS for precautions and protections. Cadmium solders should NOT be used for food or potable water applications.  


For any questions, please fill out the form below and a Kapp representative will contact you shortly.