Disclosed is a method for activating a surface of metals, such as self-passivated metals, and of metal-oxide dissolution, effected using a fluoroanion-containing composition. Also disclosed is an electrochemical cell utilizing an aluminum-containing anode material and a fluoroanion-containing electrolyte, characterized by high efficiency, low corrosion, and optionally mechanical or electrochemical rechargeability. Also disclosed is a process for fusing (welding, soldering etc.) a self-passivated metal at relatively low temperature and ambient atmosphere, and a method for electrodepositing a metal on a self-passivated metal using metal-oxide source.

The invention relates to a method for modifying piece surfaces consisting in bringing pieces into contact with at least one type of a modifying agent in such a way that the modification of the surface is carried out.

There is provided the use of at least one ionic liquid as a soldering/brazing flux. There is also provided a method of soldering a metal comprising applying a solder/braze comprising a flux to a surface of the metal and heating said metal to a desired soldering/brazing temperature, wherein the soldering/brazing flux comprises one or more ionic liquids.

A method of soldering a shape memory alloy (SMA) element to a component includes positioning a tinned end of the SMA element with respect to a surface of the component, and then directly soldering the tinned end to the surface using solder material having a low liquidus temperature of 500 F. or less when an oxide layer is not present on the SMA element. The end may be soldered using lead-based solder material at a higher temperature when an oxide layer is present. The end may be tinned with flux material containing phosphoric acid or tin fluoride prior to soldering the SMA element. The SMA element may be submersed in an acid bath to remove the oxide layer. The solder material may contain tin and silver, antimony, or zinc, or other materials sufficient for achieving the low liquidus temperature. Heat penetrating the SMA element is controlled to protect shape memory abilities.

Provided is an aluminum alloy tube with superior corrosion resistance and a joining layer for brazing. In addition, a heat exchanger using a fin which utilizes a bare material of low cost and higher availability, rather than a clad material, is provided. A manufacturing method of an aluminum alloy tube, including the steps of forming a sacrificial anticorrosion layer comprising Zn, by ark spraying Zn with purity of 95% or more, onto a surface of aluminum alloy tube with a spraying amount of 3 to 10 g/m.sup.2 and a spraying speed of 15010.sup.3 to 35010.sup.3 mm/sec; and forming a joining layer for brazing by applying a joining material for brazing comprising a mixture obtained by mixing Si powder with purity of 95% or more and flux, onto a surface of the sacrificial anticorrosion layer, so that the amount of the Si powder is 1.2 to 3.0 g/m.sup.2, is provided.

The invention concerns a flux for brazing, a process for brazing metal parts employing said flux, a flux composition containing said flux, aluminum parts coated with said flux or said flux composition, a process for brazing and a brazed metal object obtainable by said brazing process. The flux is high in KAlF.sub.4 and low in K.sub.3AlF.sub.6.

A braze tape (12) useful with superalloy materials. In one embodiment, the tape includes a layer (14) containing superalloy powder (22) in a binder (24), and a layer (16) containing boron and silicon free braze material powder (32) in a binder, joined together by a layer (18) of doubled-sided adhesive Teflon tape (46).

A method of removing a ceramic thermal barrier coating system (18). Laser energy (20) is applied to the thermal barrier coating system in the presence of a flux material (22) in order to form a melt (26). Upon removal of the energy, the melt solidifies to from a layer of slag (28) which is more loosely adhered to the underlying metallic substrate (12) than the original thermal barrier coating system. The slag is then broken and released from the substrate with a mechanical process such as grit blasting (30). Sufficient energy may be applied to melt an entire depth of the coating system along with a thin layer (34) of the substrate, thereby forming a refreshed surface (36) on the substrate upon resolidification.

A flux material that provides a heat outflow control layer of slag (30) on a melt pool (20) that suppresses lateral heat outflow (27) and facilitates uniaxial heat outflow (26A-D) from the melt pool at a rate that causes unidirectional crystallization in the melt pool to match a crystal direction (24) of a substrate (22). The slag may be insulative, and may flow to form a greater slag thickness (T2, T3) at the sides of the melt pool than at the middle (T1). The flux may contain constituents that warm the sides of the melt pool by exothermic reaction. The flux may be used in combination with insulating elements (32A-B, 38A-B, 44) placed on the substrate surface beside the melt pool and/or with supplemental heating of the sides of the weld.

Aluminum parts, e.g., heat exchangers, with improved resistance towards corrosion caused by contact with stationary water or aqueous compositions such as cooling water can be obtained by addition of Li compounds in specific amounts to the flux used for brazing the parts. LiF and especially Li fluoroaluminates are very suitable. The flux and the Li salt can be dispersed in water or an aqueous composition separately.