Технология нанесения антикоррозионных лаков на основе растворимых фторопластов

The technology of applying anti-corrosion varnishes based on soluble fluoropolymers

The technology of applying LF-32ln varnish

LF-32ln varnish is applied by dip coating, curtain coating, or by using a brush, sprayer or roller. For coating with a sprayer the varnish should be diluted with butyl acetate to a viscosity of 13 to 25 s (determined by the VZ-4 viscometer). The thickness of a single coat varies from 10 to 25 µm depending on the coating method. The recommended thickness for protection against corrosion is 100 to 150 µm. LF-32ln coatings can be obtained within the range of temperatures from +25 °C to +100 °C.

Recommendations for applying LF-32ln varnish:

  • each layer should be dried at +20-25 °C for 30-40 minutes, then heated at +50-100 °C for 30-45 minutes.

  • coatings with satisfactory adhesion to the surface being coated are produced by heat treatment of the first layer and then of the entire coating at +150-220 °C for one hour.

  • adhesion can be significantly improved if LF-32ln varnish is applied on the surface that has been sand-blasted, phosphated, chromated or covered with a butyrate phosphate or epoxy layer.

  • with a thickness of 100 µm a LF-32ln varnish coating withstands a voltage of 3,000 volts.

The technology of applying cold-curing PTFE-epoxy varnishes (LFE-42lnh, LFE-32lnh)

The item or surface should be free of dirt and rust, after which it should be sandblasted or beadblasted and degreased with acetone.

Cold-curing varnishes are applied by curtain coating, or by using a brush or sprayer.

Before adding the AF-2 (Russian code АФ-2) hardener (which is included in the price and into packaging) into the varnish, it should be diluted with twice the amount of acetone (1:2). The shelf life of the mixture of varnish and solvent is no more than two days.

The amount of hardener is calculated according to the following formula:

X = a • K, where

  • X is the mass of the hardener per 1 kg of varnish, g;

  • a is the mass fraction of solid residue, %;

  • K is the conversion factor of 0.5 for LFE-32lnh and LFE-42lnh varnishes.

Resulting compositions are brought up to a working viscosity (determined by the VZ-4 viscometer) of:

  • 20-50 s – by coating with a brush,

  • 15-40 s – by dipping,

  • 13-25 s – by coating with a sprayer.

In order to dilute LFE-32lnh and LFE-42lnh varnishes either pure butyl acetate or a mixture of the following solvents can be used:

  • Acetone – 20 % of weight;

  • Butyl acetate – 50 % of weight;

  • Ethyl acetate – 30 % of weight.

After adding the hardener and the solvent the composition is mixed, after which air bubbles are removed and the composition is filtered through a nylon or silk mesh. It is recommended to use epoxy primers for coatings that operate at elevated temperatures. PTFE-epoxy varnishes are applied on cured primers. The first layer is dried at room temperature (+15-25 °C) for 30-40 minutes, as well as all the subsequent layers. The coating is then dried in air for 3-5 days at +15-25 °C or heated at +70-80 °C for 5 hours.

A multilayer coating is stronger than a single-layer coating of the same thickness. Avoid uneven coating.

The thickness of a multilayer coating and the application method depend on operating conditions. Varnish consumption is ~200g/m2 (for a coating thickness of 100-120 µm).

The technology of applying a combination coating

In order to protect surfaces working in harsh conditions from corrosion it is recommended to use a combination coating. The pre-treated surface is covered with one or two layers or the EP-00-10 primer (Russian code ЭП-00-10). The cured primer is coated with PTFE-epoxy varnish LFE-32lnh (coating thickness 30-50 µm). The first layer of coating is dried at room temperature (+15-25 °C) for 30-40 minutes, as well as all the subsequent layers. Then PTFE varnish LF-32ln is applied, the layer of which is dried at +50-100 °C for 30-45 minutes.

A multilayer coating is stronger than a single-layer coating of the same thickness. Avoid uneven coating.

The thickness of a multilayer coating varies from 30 to 150 µm depending on operating conditions. The thickness of a single-layer coating varies from 10 to 30 µm depending on the method of coating. Varnish consumption is ~200g/m2 (for a coating thickness of 100-120 µm).