Hydrochloric nickel-based alloys

Pla.tinum, Platinum plating has found appHcation in the production of platinised titanium, niobium, or tantalum anodes which are used as insoluble anodes in many other plating solutions (see Metalanodes). Plating solutions were often based on platinum "P" salt, which is diamminedinitroplatiniim (IT). A dinitroplatinite sulfate—sulfuric acid bath has been used to plate direcdy onto titanium (129). This bath contains 5 g/L of the platinum salt, pH adjusted to 2.0 with sulfuric acid. The bath is operated at 40°C at 10—100 A/m. Other baths based on chloroplatinic acid have been used in both acid and alkaline formulations the acid bath uses 20 g/L of the platinum salt and 300 g/L hydrochloric acid at 65° C and 10—200 A/m. The alkaline bath uses 10 g/L of the platinum salt, 60 g/L of ammonium phosphate and ammonium hydroxide to give a pH of 2.5—9.0. The alkaline bath can be plated directly onto nickel-base alloys acid baths require a gold strike on most metals. 

Sulfite pulping chemical recovery consists of greater amounts of sulfite, hydrogen sulfide, and hydrochloric acid than those used in the Kraft process. Because of these corrosive species, the internal portions of the recovery boilers and the evaporators are generally constructed of reinforced plastics, type 316L stainless steel, type 317L stainless steel, or nickel-based alloys. To prevent pitting and crevice corrosion, scale build-up should be prevented, wet-dry zones should be avoided, and chloride concentration should be kept to a minimum. 

The influence of alloying elements in cobalt-based alloys seems to be the same as for nickel-based alloys. Table 2-14 shows that in boiling hydrochloric and sulfuric ac-... 

The corrosion behavior of non-ferrous alloys such as those based on nickel, cobalt, copper, zirconium, and titanium has been reviewed in detail in this chapter. Besides exotic materials such as tantalum and platinum, nickel-based alloys are the most resistant to corrosion by mineral acids, and they are especially resistant to localized corrosion in chloride-containing environments, which troubles stainless steels. Nickel-based alloys can broadly be divided into alloys, e.g. Ni-Mo (B-2, B-3) and Ni-Cu (alloy 400), that do not contain chromium, and are not, therefore, passivated under oxidizing conditions, and alloys, e.g. Ni-Cr-Mo (C-22, C-2000,59,686, etc.) and Ni-Cr-Fe (G-30, 825, etc.), that form a chromium oxide passive film under oxidizing conditions. Ni-Mo alloys such as B-3 have excellent corrosion resistance in hot reducing acids such as hydrochloric and sulfuric. Ni-Mo alloys cannot withstand oxidizing conditions such as nitric acid and hydrochloric acid contaminated with ferric ions. Ni-Cr-Mo alloys such as C-2000 alloy are multipurpose alloys that can be used both in reducing and oxidizing conditions. 

Resistance to aqueous solutions is good in organic acids, sulfuric and hydrochloric acid at temperatures below 150°F (65°C), as well as a variety of other applications. Satisfactory resistance has also been exhibited to hydrofluoric acid. Although nickel-based alloys are not normally used in nitric acid service, alloy 625 is resistant to mixtures of nitric-hydrofluoric acids, in which stainless steel loses its resistance. 

Shipment nd Stora.ge, Sulfur monochloride is minimally corrosive to carbon steel and iron when dry. If it is necessary to avoid discoloration caused by iron sulfide formation or chloride stress cracking, 310 stainless steel should be used. Sulfur monochloride is shipped in tank cars, tank tmcks, and steel dmms. When wet, it behaves like hydrochloric acid and attacks steel, cast iron, aluminum, stainless steels, copper and copper alloys, and many nickel-based materials. Alloys of 62 Ni—28 Mo and 54 Ni—15 Cr—16 Mo are useful under these conditions. Under DOT HM-181 sulfur monochloride is classified as a Poison Inhalation Hazard (PIH) Zone B, as well as a Corrosive Material (DOT Hazard Class B). Shipment information is available (140). 

Hydrochloric acid as a hydrolyzer and as a product of hydrolysis in the absence of alkali has been the source of much trouble as it is one of the most corrosive chemicals known. However, even at slightly elevated temperatures, completely dry hydrogen chloride gas has very little corrosive action and is easily handled in iron equipment. Nickel and Monel metal are fairly resistant to low hydrochloric acid concentrations. With dilute acid,. several of the copper-base alloys, si ch as phosphor bronze, aluminum bronze, manganese bronze, ahd Everdur metal, have fairly good... 

A more universal method of SpAs preparation is based on reduction of IcP bases (e.g., 2, 327 and 330) instead of the IcP quaternary salts mentioned above. The reduction was performed with nickel aluminium alloy or, better still, with a mixture of formic acid and triethylamine. In the latter case, reaction results in the formation of isolable 5-formyl SpAs derivatives (e.g., 554 and 555) readily hydrolyzed in hot hydrochloric acid to SpAs in 85-95% yield, unsubstituted (493) or substituted (556 and 557) at the ring nitrogen atoms. By this method, the previously unknown 2-aza-SpA 558 were prepared from l,2,3-triazolo[4,5-c]pyridine (2002ZOR440). 

Materials classes that were tested included ceramics, nickel-based and cobalt-based alloys, refractory metals and alloys, reactive metals and alloys, noble metals and alloys, and high-temperature polymers, a total of 26 materials. Test periods varied between 37.5 and 47.5 hours. None of the materials was found to be suitable for all test conditions, and most exhibited moderate (equivalent to between 10 and 200 mil per year) to severe (>2()0 mil per year) corrosion. Titanium and titanium alloys (Nb/Ti and Ti-21S) exhibited the best performance, showing only slight corrosion in the presence of excess sodium hydroxide. Under acidic conditions, titanium showed increased rates of corrosion, apparently from attack by sulfuric acid and hydrochloric acid. Both localized pitting and wall thinning were observed. 

Hydrochloric acid and even brines are so troublesome that scarcely any entirely satisfactory materials are available. Among the best materials are metallic silver or tantalum and glass or ceramics ware. For dilute acid or brines, the standard materials are the copper-base alloys or nickel alloys (see Table 9-4). 

The endpoint for copper on zinc-base or aluminum alloys is marked by the appearance of a black spot, and on nickel by a white spot. When testing copper on steel, the endpoint is detected as a black spot by placing with a pipette two drops of a 1 % antimony oxide solution in 50 % concentrated hydrochloric acid on the test area at interveils during the test. It is not required for bronze on steel. 

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