GB/T 9989.5-2015Vitreous and porcelain enamels -- Determination of resistance to chemical corrosion -- Part 5: Determination of resistance to chemical corrosion in closed systems (English PDF)

Foreword

GB/T 9989 "Determination of enamel resistant to chemical attack" is divided into five parts.

--- Part 1. Determination of acid erosion at room temperature;

--- Part 2. resistant to boiling acids, boiling neutral liquids and their vapors Determination of chemical attack;

--- Part 3. Hexagonal alkali solution container was measured erosion;

--- Part 4. a cylindrical container with a solution of alkali was measured erosion;

--- Part 5. Determination of resistance to chemical attack in a closed system.

This part of GB/T 9989 Part 5.

This section drafted in accordance with GB/T 1.1-2009 given rules.

This section uses the translation method identical with ISO 28706-5:2010 Determination of chemical attack "enamel resistance - Part 5. in a closed system Determination of resistance to chemical attack "(in English).

Consistency correspondence between this part of international documents and normative references of our files are as follows.

Laboratory use specifications and test methods (. 1987, MOD ISO 3696) --- GB/T 6682-2008 analysis.

This part is proposed by the China National Light Industry Council.

This part of the National food in direct contact with materials and products Standardization Technical Committee (SAC/TC397) centralized.

This section is drafted. Donghua University, the National Optical glass enamels Quality Supervision and Inspection Center.

Introduction

Aqueous solution of enamel and enamel erosion is a process of dissolution. Enamel main component is silica, it forms a three-dimensional silica Salt network, formed by the hydrolysis of silicic acid or silicates, silicic acid or silicates dissolve these to erode medium. Other components (mainly gold Metal oxide) will be hydrolyzed to form the corresponding metal hydroxide or hydroxide ions. All the products are eroded more or less to dissolve Aggressive medium, the whole process will lead to erosion of material per unit area of \u200b\u200bweightlessness.

Some erosion and water erosion of the enamel surface was linear with time; there are also some erosion of the enamel surface water Erosion time logarithmic relationship. Only water erosion linear relationship, you can use the scientific method to accurately calculate the weight loss per unit area Rate [g/(m2 · h)], and the erosion rate (mm/a).

Effect of water on the surface of enamel erosion is the most important factor enamel mass, temperature and pH. Limited solubility of silica Also played a certain extent. Here are erosion under different conditions in different types of enamel erosion.

a) at a temperature of 80 °C, similar to 0.1mol/L sodium hydroxide alkaline solution (see GB/T 9989.4, Chapter 9), enamel Silicate network by a greater erosion, silicates and most other components are dissolved in an alkaline hydrolysis solution, the amount of erosion and the test time is linear, and therefore, the test results can be (per unit area and per unit of time with weight loss rate per unit area of Weightlessness) and erosion rate (mm/a) to represent.

b) at room temperature, similar to the citric acidic solution (see GB/T 9989.1, Chapter 9) or similar strong sulfuric acid solution Liquid (see GB T 9989.1, Chapter/Section 10), enamel silicate network by the small erosion in the enamel deposited on the surface in addition to two Other than the silicon oxide component is limited. After high acid test by enamel, the enamel surface was not observed significant changes. and After the acid test by poor enamel, the enamel surface will produce signs of erosion or rendered rough.

c) boiling in an acidic solution (see GB/T 9989.2), enamel silicate network eroded, silica and other enamel Components are dissolved into the solution, but lower the solubility of silica in the acidic solution. Erosion solution will be dissolved dioxide Silicon quickly saturated, there is deposited only on the enamel surface. Acid erosion will be inhibited, significantly decreased the rate of erosion.

Note. The test apparatus under glass in an acid attack will release silicate, also play a role in suppressing erosion.

In the gas phase experiments, the condensate formed in the surface of the sample does not contain any dissolved components of the enamel, effectively preventing such corrosion inhibition Role.

The following are examples of non-linear enamel erosion and linear erosion.

1) boiling citric acid (see GB/T 9989.2, Chapter 10) and 30% boiling sulfuric acid (see GB/T 9989.2, Chapter 11) Since the gas phase containing only trace amounts of acid, usually only test phase. Inhibitory Effect of acid erosion, and and the amount of erosion depends on the time trial, so the test results with weight loss per unit area is represented; it can not be calculated Weight loss rate per unit area.

Boiling hydrochloric acid (see GB/T 9989.2, Chapter 122) 20%) Since this is an azeotropic boiling acid concentration in the liquid phase and gas phase are the same, so no liquid phase test Experience. Intense boiling provides no inhibitory aggregates, the amount of time and erosion test is linear, because Here, the test results for the weight loss rate per unit area (weight loss per unit area and per unit time) and the erosion rate (Mm/a) to represent.

d) test liquid (see GB/T 9989.5) at high temperature and pressure conditions, the acidic solution is severe erosion. To avoid production Health inhibition test time is limited to 24h, the higher the rate of acid erosion of enamel surface (simulation in a chemical reaction vessel in addition, under these conditions the test conditions), with only a low silicon content of the aqueous test solution was prepared, and erosion test Room was a linear relationship. Thus, 20% hydrochloric acid (see GB/T 9989.5, Chapter 8), simulation test solution (see GB/T 9989.5, Chapter 10) or process fluid (see GB/T 9989.5, Chapter 11) The test results can follow weight loss rate per unit area (Weight loss per unit area and per unit time) to represent.

e) in boiling water (see GB/T 9989.2, Chapter 13), the silicate network is very stable. Enamel surface to penetrate the main Lord, the amount of dissolved silica is very limited. Such erosion can be represented by a gas attack, in the liquid phase for high corrosion resistance Enamel, anti-erosion ability. But if the enamel chemical stability tests are relatively poor, the enamel surface will have an alkali metal ion analysis Out, thereby increasing the pH value of the solution, it increases the erosion of the liquid, so that liquid and vapor are able to get useful information.

f) due to erosion may be linear or non-linear, the test results for weight loss per unit area is represented, and the test should be given time.

g) For the standard detergent solution Test time 24h or 168h (see GB/T 9989.3, Chapter 9) test, because you can not really Whether a given erosion curve is linear, so can not be included in the test report erosion rate calculations.

h) For other acidic solution (see GB/T 9989.2, Chapter 14) and an alkaline solution (see GB/T 9989.3, Chapter 10 GB T 9989.4, Chapter/Section 10), because during the test did not know whether the erosion rate is linear, so in this standard the test report can not contain the erosion rate calculations.

For the firing temperature is lower than 700 °C enamel material, GB/T 9989 test parameters (medium, temperature and time) is not appropriate for in this type of enamel (such as aluminum enamel) should use other media, temperature, and (or) time. These tests can under Part 1 GB/T 9989 of Points, Part 2, Part 3 "Additional test solution" and Part 4 of the procedure described for.

Determination of enamel resistant to chemical attack Part 5. Determination of resistance to chemical corrosion in closed systems Warning. If you do not take adequate security measures, GB/T 9989 this part of chemicals and (or) the steps required for use, maybe it will be detrimental to health. This section GB/T 9989 does not address any health hazards involved in this section, safety or environmental issues. use GB/T 9989 this part of the Notes should be developed for health, safety and environmentally acceptable, and our compliance with the relevant regulations and international set. Comply with GB/T 9989 This part can not serve as the legal basis for exemption.

1 Scope

This section provides a mixture of determination of the acid resistance of enamel products in a closed system, the neutral and alkaline solutions, as well as the actual process agreed Test method body erosion.

This method is mainly used to test the performance of the enamel used in chemical processing (process) in.

2 Normative references

The following documents for the application of this document is essential. For dated references, only the dated version suitable for use herein Member. For undated references, the latest edition (including any amendments) applies to this document.

ISO 649-1 Laboratory glassware Universal hydrometer - Part 1. Specification (Laboratoryglassware-Density hydrometersforgeneralpurposes-Part 1. Specification) ISO 3696 for analytical laboratory use specifications and test methods (Waterforanalyticallaboratoryuse-Specification andtestmethods) Principle 3 Under specified conditions, the enamel sample is placed in the autoclave, the normal boiling point of the liquid in the erosion be more aggressive.

Determination of weight loss, and calculated the rate of weight loss per unit area.

4 Device

Warning --- test container may be a pressure vessel, the use of this standard should be developed with the health, safety and environmental precautions to adapt Item, and compliance with our country and international regulations concerning the safe use of the pressure vessel.