The curing agent has a great influence on the physicochemical properties of polyurethane powder coatings. If the selected curing agent and resin cannot produce cross-linking reaction well, the physicochemical properties of polyurethane powder coatings will be affected to a great extent.
The powder coating film is tested for: aging resistance, gloss, cupping and other various physicochemical properties, and a more excellent one is selected as the final curing agent for the polyurethane powder coating.
The curve 3 hardly changes. Curve 2 and curve 3 intersect at s’. Because the corrosion inhibitor is added to the corrosive medium, the metal corrosion potential is shifted from pe to pl and enters the passivation zone, and the corrosion current density becomes, i<ic.
The addition of this type of corrosion inhibitor increases the anode polarization, reduces the speed of the anode reaction, and strongly inhibits the corrosion of the metal. The effect of this corrosion inhibitor is caused by the reduction of the anode reaction rate. Another situation is that after the anode type corrosion inhibitor is added to the corrosive medium, the metal surface does not necessarily appear to be transformed, but the metal is corroded. The potential has moved in the positive direction, which increases the Tafel slope of the anode polarization curve, as shown in Figure 22-2. This situation can also slow down the corrosion of the metal. Phosphates, silicates, borates, carbonates, benzoates, polycinnamates, etc. have corrosion inhibitory effects on metals, but they have no oxidizing properties and must act as corrosion inhibitors. To use, there must be dissolved oxygen in the solution. These corrosion inhibitors are mostly strong bases and weak acid salts, which are hydrolyzed in water to produce hydroxide ions, and are on the metal surface.
Passivation oxides are formed on the 18th surface of the station, and lgi are used to effectively prevent the polarization curve corrosion of iron and its alloys. When OH~ is sufficient, only the oxygen of OH~ can form a passivation oxide.
The role of this type of corrosion inhibitor is not only to increase the concentration ptfe powder cost per kg of OH-1, but also to promote the formation of a passivation layer. The name is 0.7N aSiO; and Nas PO, both are alkaline corrosion inhibitors, but both The effect on 1.1 carbon steel anode dissolution is not the same: phosphate can passivate the steel, 1.5-6-5-4-2 and silicate can make the steel in a very wide 1gi/(A/cm²)
Activation in the potential zone. This shows the effect of the anionic characteristics of the passivation 22-3 on the passivation of steel 2! The treatment is not only to change the pH. In 1 a base solution (borax buffer 10 0.025ml/L
In this case, it can also be blunt Nag50s, pH=7.1);
Anion 2 of the corrosion inhibitor +0.03mol/l.N aSiO is found in the chemical film;
3 a bottom solution +0.03mol/1.Na gPO: ion.
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