*2.1.5. Solution temperature*

The solution temperature affects several physical properties of the suspension (such as the viscosity and the sedimentation rate) and influences the reduction kinetics of the free and adsorbed cations as well as the possible adsorption of particles on the cathode [27]. Although there are few works in the literature studying the effects of this parameter in the electrochem‐ ical codeposition process, these works show the relationship between the solution temperature and the increase of codeposited particles in metallic matrix or the morphology of the coating. Thus, this parameter is still scarcely explored and understood.

The temperature of 50°C was considered the most beneficial one for the incorporation of alumina particles in Co-Ni matrix from an acidic Ni(II)/Co(II) sulfamate bath instead of 60°C [12]. For the codeposition of alumina particles in Cr matrix from a sulfate bath containing a rare earth element (not mentioned), the best temperature range for particle incorporation was from 30°C to 40°C. When the temperature was below 30°C, the composite coating was rough, whereas, when it was above 40°C, the composite coating decreased; beyond 55°C, there was no Al2O3 codeposited with Cr [55].

Research works carried out for Zn-SiC composite coatings [56] showed that the increase of solution temperature (33–45ºC) caused a significant reduction of particle content in the coating. The authors considered that the increase in the solution temperature favored the electroactive species reduction, while it did not increase the codeposition of the SiC particles. Kim and Yoo [48] verified the same behavior for Ni-SiC composite coatings.

It is important to mention that the overall result concerning the temperature variation on the codeposition process for producing MMC coatings is difficult to predict, as the parameter most affected by the solution temperature is not generally identified in the usual used deposition mechanisms [12,27].
