Treatment method for making heat exchanger hydrophilic and heat exchanger treated to be hydrophilic

A treatment method for making a heat exchanger hydrophilic comprising previously performing the pickling treatment for a heat exchanger by any of the following methods (1) to (4), and performing a chemical transformation treatment to form a chemical conversion coating film with a zirconium series treatment agent, followed by the treatment for making said heat exchanger hydrophilic using the following treatment agent for hydrophilicity, so that the amount of coating film becomes 0.1 to 3 g/m2, wherein:

• “treatment agent for hydrophilicity” means a treatment agent which contains silica particulates and polymers of vinyl alcohol series in the weight ratio in the range 30:70˜70:30 in aqueous medium, amounting to 0.2˜25 weight percent in total for both, in which said silica particulates are coated with said polymer of vinyl alcohol series, and dispersed in the aqueous medium as coated particles having the average particle diameter of 5 nm to 1000 nm, wherein said method comprises:
• (1) a pickling method for a heat exchanger made of aluminum materials, wherein a cleaning treatment is performed by bringing said heat exchanger into contact with a pickling agent containing at least one acid selected from a group consisting of nitric acid, sulfuric acid and hydrofluoric acid, and iron salt prior to the chemical transformation treatment applied to said heat exchanger;
• (2) the pickling method according to the aforementioned (1), wherein said iron salt is iron sulfate, iron nitrate, iron acetate or iron chloride;
• (3) the pickling method according to the aforementioned (1) or (2), wherein said pickling agent contains an iron salt in the range 0.01 to 5 weight percent;
• and
• (4) the pickling method according to the aforementioned (3), wherein said cleaning treatment comprises bringing said heat exchanger into contact with said pickling agent under the conditions at 10 to 85° C. for 30 seconds to 5 min.

A treatment method for making a heat exchanger hydrophilic comprising the steps of:

• brining a heat exchanger made of aluminum materials into contact with a pickling agent containing at least one acid selected from a group consisting of nitric acid, sulfuric acid and hydrofluoric acid so as to clean the heat exchanger;
• performing a chemical transformation treatment to the heat exchanger for forming a chemical conversion coating film;
• and then
• applying a treatment agent for hydrophilicity onto the heat exchanger for producing a hydrophilic coating film thereon so as to make the heat exchanger for producing a hydrophilic coating film thereon so as to make the heat exchanger hydrophilic, the treatment agent for hydrophilicity containing silica particulates and a polymer of vinyl alcohol series in an aqueous medium, wherein the silica particulates are coated with the polymer of vinyl alcohol series and dispersed in the aqueous medium.

A hydrophilic heat exchanger made by a method comprising the steps of:

• brining a heat exchanger made of aluminum materials into contact with a pickling agent containing at least one acid selected from a group consisting of nitric acid, sulfuric acid and hydrofluoric acid so as to clean the heat exchanger;
• performing a chemical transformation treatment to the heat exchanger for forming a chemical conversion coating film;
• and then
• applying a treatment agent for hydrophilicity onto the heat exchanger for producing a hydrophilic coating film thereon so as to make the heat exchanger hydrophilic, the treatment agent for hydrophilicity containing silica particulates and a polymer of vinyl alcohol series in an aqueous medium wherein the silica particulates are coated with the polymer of vinyl alcohol series and dispersed in the aqueous medium;
• wherein the hydrophilic heat exchanger has the hydrophilic coating film containing the polymer of vinyl alcohol serving as a medium and a plurality of the silica particulates dispersed in the medium.