Chromium coatings electrolyte

Electrodeposited chromium coatings. Electrolytic corrosion testing Coatings cathodic to the substrate-rating of electroplated test specimens subjected to corrosion tests... 

Electrodeposited chromium coatings—Electrolytic corrosion testing (EC test)... 

Tin Free Steel—Electrolytic Chromium-Coated. A less expensive substitute for tinplate, electrolytic chromium coated-steel, has been developed and is designated TFS-CT (tin free steel-chromium type) or TFS-CCO (tin free steel-chromium-chromium oxide) (19). This material can be used for many products where the cathodic protection usually supplied by tin is not needed. A schematic cross section is shown in Figure 2. Electrolytic, chromium-coated steel is made by electro-lytically depositing a thin layer of metallic chromium on the basic tin mill steel, which is in turn covered by a thin passive coherent layer of chromium oxide. 

Where the corrosion resistance of a coating depends upon its passivity, it is common to follow plating with a conversion coating process to strengthen the passive film. Zinc, cadmium and tin in particular are treated with chromate solutions which thicken their protective oxides and also incorporate in it complex chromates (see Section 1S.3). There are many proprietary processes, especially for zinc and cadmium. Simple immersion processes are used for all three coatings, while electrolytic passivation is us on tinplate lines. Chromate immersion processes are known to benefit copper, brass and silver electrodeposits, and electrolytic chromate treatments improve the performance of nickel and chromium coatings, but they are not used to the extent common for the three first named. 

The most common metal materials used for metal food cans are aluminum, tinplate, and electrolytic chromium-coated steel. The traditional cylindrical can is a three-piece can widely used for heat-processed foods, which consists of the can body and... 

The most developed application of UDD is their use for strengthening composite electrochemical chromium-based coatings. Ultradisperse diamond is introduced into the standard chromium-plating electrolyte usually as suspension. The... 

Closely related to electrorefining is electroplating, the coating of one metal on the surface of another using electrolysis. For example, steel automobile bumpers are plated with chromium to protect them from corrosion, and silver-plating is commonly used to make items of fine table service. The object to be plated is carefully cleaned and then set up as the cathode of an electrolytic cell that contains a solution of ions of the metal to be deposited. 

Aluminum, chromium, titanium, and several other metals can be colored by an electrochemical process called anodizing. Unlike electroplating, in which a metal ion in the electrolyte is reduced and the metal is coated onto the surface of the cathode, anodizing oxidizes a metal anode to yield a metal oxide coat. In the oxidation of aluminum, for instance, the electrode reactions are... 

Noble metal coatings (e.g., nickel) can be effective, but only if they remain unbroken and are of sufficient density and thickness. Electrolytic deposits of tin, lead, copper or silver on steel are also considered as protectors and probably do not modify the normal features of fatigue because they suppress contact with the surrounding environment. Observations made on the use of deposits of nickel or chromium are contradictory.7... 

X Alloys, including stainless steel, batteries, chemicals, catalysts and the electrolytic coating of items such as chromium-plated taps and fittings used for tap water 23, 3529, 37, 38... 

Up until now, there has been little interest in electrolytic deposition of iron metals and chromium from nonaqueous solutions, because such deposits are easily obtained from aqueous electrolytes. On the other hand, adhesive layers can be applied to reactive metals like titanium, beryllium, and magnesium, for example through nickel deposition from nonaqueous solutions. By depositing such metals out of nonaqueous solutions, hydrogen sensitive materials, such as low-alloy high-strength steel, can be coated without danger of embrittlement. Materials coated in this way with a compact poreless metal layer can be further coated in an aqueous electrolyte. 

Chromium electrodeposits can also be obtained from electrolytes containing acetone and chromium chloride at current densities of 0.1-1 A/dm and 15 °C. Nickel-chromium alloy coatings with up to 22% chromium can be deposited out of... 

The efficiency of the electrolytic oxidation is limited to some extent by the reduction of chlorate at the cathode. To check this reduction as far as possible, a little chromate or dichromate is added to the bath. This is partially reduced at the cathode to tripositive chromium, which forms a coating of a chromic chromate around the cathode and thus inhibits the cathodic reduction of chlorate or hypochlorite. 

Finely divided electrolytic chromium metal [Alfa Products] (1.306 g, 25.1 mmol) is placed in a three-necked 500-mL flask containing a Teflon-coated stirring bar with 50 mL of absolute ethanol, and the N2 gas is bubbled through the solvent for 20 min. The chromium metal is dissolved completely by passing anhydrous HCI gas under reflux through the alcohol until a deep-blue sohAion is obtained. The addition of HCI is then stopped while N2 gas is bubbled through the solution. 

Bright surfaces can be obtained by polishing or by using bright nickel electrolytes. However, in industrial atmospheres, tarnishing will occur. Therefore, in many cases, a thin chromium layer is plated above the nickel coating with thickness between 0.25 and 1.5 xm (see Sect. 5.5.4.3). The presence of the... 

---