Soldering other precipitation may wash the lead into the groundwater. Unfortunately, most lead-free solders are not eutectic formulations, melting at around , making it more difficult to create reliable joints with them. Other common solders include low-temperature formulations (often containing bismuth), which are often used to join previously-soldered assemblies without unsoldering earlier connections, and high-temperature formulations (usually containing silver) which are used for high-temperature operation or for first assembly of items which must not become unsoldered during subsequent operations. Alloying silver with other metals changes the melting point, adhesion and wetting characteristics, and tensile strength. Of all the brazing alloys, silver
Dry lubricant room temperature to form a solid lubricant. Pastes are grease-like lubricants containing a high percentage of solid lubricants used for assembly and lubrication of highly loaded, slow-moving parts. Black pastes generally contain MoS. For high temperatures above 500 °C, pastes are composed on the basis of metal powders to protect metal parts from oxidation necessary to facilitate disassembly of threaded connections and other assemblies. Dry-powder tumbling is an effective application method. The bonding can be improved by prior phosphating of the substrate. Use of free powders has its limitations, since adhesion of the solid particles to the substrate is usually