Pilot plant production of black chrome in Thailand: from science to technology

An effort to transfer the technology of black chrome selective surfaces from the laboratories in industrial countries to a developing country has been carried out at King Mongkut's Institute of Technology Thonburi, Thailand. The first phase of the study is aimed at reproducing the findings obtained previously on the laboratory scale by others using the Harshaw (now Englehard Industries, Cleveland, OH, USA) Chromonyx TM process. The search for the optimum deposition conditions was performed employing a novel gradient search method. The radiative properties and the stability of the black chrome surfaces are reproducible. The second phase involved the subsequent development of these initial efforts into the larger scale of pilot plant production. A pilot scale black chrome plating unit has been designed and entirely constructed from technology indigenous to Thailand. The unit can electroplate black chrome on 1.5 × 10 dm 2 (10 dm = 1 m) aluminium substrates on a semicontinuous basis. The radiative properties of the coated surfaces averaged over the entire 15 dm 2 area are α s = 0.97 and ϵ t = 0.17. The uniformity of the plating indicated by the variation of the ϵ t values is good with reproducibility of ±0.015. Economic analysis of a plant designed to produce 17 300 m 2 per year gives a payback time of 3.5 years, assuming the economic conditions of Thailand in 1985. Our successful development of a pilot plant to manufacture black chrome is useful to other countries of comparable resources.