Method and device for preparing high strength and durable super-hydrophobic film layer on inner wall of elongated metal tube

A method for preparing a high-strength and durable super-hydrophobic film layer on an inner wall of an elongated metal tube, comprising steps of:

• roughening treatment of the inner wall of the elongated metal tube comprising:
• etching the inner wall of the elongated metal tube with 2 mol/L to 4 mol/L of nitric acid or 2 mol/L to 4 mol/L of hydrochloric acid for 5 min to 30 min, so that a rough structure is formed on the inner wall of the elongated metal tube;
• and exposing an active surface of the inner wall of the elongated metal tube;
• preparation of a nickel-phosphorus alloy layer comprising:
• depositing the nickel-phosphorus alloy layer on the inner wall of the rough metal tube by use of an electroless plating method, wherein:
• a first plating solution used in the electroless plating method comprises:
• 0.1 mol/L to 1 mol/L of nickel chloride hexahydrate, 0.1 mol/L to 1 mol/L of sodium hypophosphite, 0.1 mol/L to 1 mol/L of trisodium citrate and 0.001 mol/L to 0.01 mol/L of brightener;
• and a temperature of a first plating bath is from 60° C. to 90° C.;
• preparation of a functional coating comprising:
• electrodepositing a functional coating on the nickel-phosphorus alloy layer, wherein:
• an electrodeposition bath is operated under an ultrasonic environment to form a micron- or submicron-sized channel structure;
• a second plating solution used for electrodeposition of the functional coating comprises:
• 0.01 mol/L to 0.1 mol/L of nickel sulfate hexahydrate, 0.1 mol/L to 1 mol/L of nickel chloride hexahydrate, 0.1 mol/L to 1 mol/L of boric acid, 0 mol/L to 0.1 mol/L of silica particles and 0.001 mol/L to 0.05 mol/L of amphiphilic substance;
• a temperature of a second plating bath is from 15° C. to 50° C.;
• an ultrasonic frequency for the second plating bath is from 20 kHz to 60 kHz;
• and a power is from 150 W to 400 W;
• performing heat treatment on a surface of the functional coating at a temperature from 100° C. to 350° C. for 0.5 h to 2 h;
• performing anodization comprising:
• inserting a nickel wire as a cathode into a cavity of the elongated metal tube and the elongated metal tube as an anode into a third solution;
• anodizing under a condition of fluid circulation at room temperature for 1 min to 10 min, and an applied voltage of 1 V to 5 V, wherein a composition of the third solution comprises 0.25 mol/L to 0.1 mol/L of potassium chloride at pH of 2.0 to 6.0;
• and
• performing a low surface energy modification with a mixed solution of ethanol-water dissolved with a low surface energy substance, wherein:
• a mass ratio of ethanol to water in the mixed solution of ethanol-water is from (1:9) to (9:1);
• a temperature of the mixed solution of ethanol-water is from 60° C. to 90° C.;
• and a time of the low surface energy modification is from 1 hour to 3 hours.