In the cyanidation process of gold , impurities can form various films on the surface of gold particles and affect the dissolution rate of gold. The resulting film and its effect on the dissolution rate of gold are as follows: 1. sulfide film    In the cyanide solution, when the sulfur ion concentration reaches 0.5 ppm , the dissolution rate of gold is lowered. This is due to the formation of an insoluble gold sulfide film on the surface of the gold particles which hinders the continued dissolution of gold. 2. Hydrogen peroxide film    When calcium hydroxide is used as a protective base, a calcium peroxide film is formed on the surface of gold to hinder the action of gold and cyanide. This can be thought of as the formation of lime and H 2 O 2 accumulated in solution as follows:   Ca(OH) 2 +H 2 O 2 → CaO 2 +2H 2 O 3. Oxide film    When ozone is added to the cyanide solution, a brick red gold oxide film is formed on the surface of the gold to reduce the dissolution rate of gold. 4. Insoluble oxide film    Appropriate amount of Pb 2+ has a growth-increasing effect on the dissolution of gold, and when it is excessive, it causes a blocking effect. This is because lead and gold form a primary battery, and gold becomes an anode in the primary battery, so gold is transferred to the solution. Excess Pb 2+ will deposit as an insoluble Pb(CN) 2 film on the surface of gold . 5. Xanthate gold film    When the flotation concentrate is cyanated, the concentration of gold in the cyanide solution exceeds 0.4 ppm , and the dissolution rate of gold decreases. This is due to the formation of a gold film of xanthate on the surface of gold. In order to overcome this adverse effect, in the case of ensuring the flotation recovery rate, the amount of the flotation agent is reduced as much as possible, and the drug is removed before the flotation concentrate is cyanated. Backing Ring Flange usually is for thin flanges with very small thickness and flanges norms have BS10 Table D, SANS1123 1000/3, ANSI B16.5 and PE PN16, backing ring flanges usually using in HDPE pipe connection and not for welding connection, also backing rings usually covered galvanizing, hot dipped galvanized backing ring and cold galvanized. Backing Ring Flange Backing Ring Flange,Br Flange,Hot Dipped Galvanizing backing ring,Backing Ring zinc coated, backing ring manufacturer Jinan Hyupshin Flanges Co., Ltd , https://www.iflange.com