GB/T 9989.3-2025Vitreous and porcelain enamels - Determination of resistance to chemical corrosion - Part 3: Determination of resistance to chemical corrosion by alkaline liquids using a hexagonal vessel or a tetragonal glass bottle (English PDF)

Foreword

This document complies with the provisions of GB/T 1.1-2020 "Standardization Work Guidelines Part 1: Structure and Drafting Rules of Standardization Documents". Drafting.

This document is Part 3 of GB/T 9989, "Determination of Chemical Resistance of Enamel". GB/T 9989 has already published the following parts.

---Part 1: Determination of acid resistance at room temperature;

---Part 2: Determination of resistance to chemical corrosion from boiling acids, boiling neutral liquids, alkaline liquids and their vapors;

---Part 3: Determination of resistance to chemical attack by alkaline solutions using hexagonal or quadrangular glass containers;

---Part 4: Determination of resistance to alkaline solution corrosion using cylindrical containers;

---Part 5: Determination of resistance to chemical attack in closed systems.

This document replaces GB/T 9989.3-2015 "Determination of Chemical Resistance of Enamelware - Part 3: Alkali Solution Resistance Using Hexagonal Containers".

The main technical changes in "Determination of Erosion" compared to GB/T 9989.3-2015, apart from structural adjustments and editorial modifications, are as follows.

a) The temperature requirement in the range has been removed (see Chapter 1);

b) Acetic acid solution reagent was added (see 5.8);

c) The number of sealing rings has been changed (see 6.1.6, 5.1.6 in the 2015 version);

d) The experimental apparatus "quadrilateral glass container" and its experimental procedures have been added (see 6.2, 8.3).

This document is modified to adopt ISO 28706-3:2017 "Enamelled porcelain - Determination of resistance to chemical attack - Part 3: Chemical attack using hexagonal or quadrangular glass containers".

Determination of the resistance of glass containers to chemical corrosion by alkaline solutions.

The technical differences between this document and ISO 28706-3:2017, and the reasons therefor, are as follows.

a) The scope of application has been changed to suit my country's technological conditions (see Chapter 1);

b) ISO 3696 (see 5.1) has been replaced with the normatively referenced GB/T 6682 to adapt to my country's technical conditions and increase operability. Actual nature;

c) ISO 48 (see 6.1.1, 6.2.1) has been replaced with the normatively referenced GB/T 6031 to adapt to my country's technical conditions and to add [further details needed]. Operability;

d) The number of sealing rings was changed (see 6.1.6) to adapt to my country's technical conditions and increase operability;

e) ISO 3585 (see 6.2.1, 6.2.5, 6.2.6) has been replaced with the normatively referenced GB/T 34843 to adapt to my country's technical requirements. Add components to increase operability;

f) ISO 4799 has been replaced with the normatively referenced GB/T 28212 (see 6.2.5) to adapt to my country's technical conditions and increase operability. Actual nature;

g) ISO 28764 (see Chapter 7) has been replaced with the normatively referenced GB/T 38166 to adapt to my country's technical conditions and add [further details needed]. Operability;

h) The oven temperature was changed to 120°C±5°C (see 8.3), consistent with the oven temperature conditions in 8.2, increasing operational uniformity and operability. Comparison of sexes. The following editorial changes have been made to this document.

---The national standard cited in the introduction replaces the international standard GB/T 9989.1-2015, replacing ISO 28706-1:2008.

GB/T 9989.2-2025 replaces ISO 28706-2:2017; GB/T 9989.5-2015 replaces ISO 28706-5:2010.

---Notes 1 and 2 in Chapter 1 of ISO 28706-3:2017 have been deleted (see Chapter 1);

---The note in Chapter 4 of ISO 28706-3:2017 has been removed (see Chapter 4);

---The phrase "such as distilled water or water of equivalent purity" has been removed from section 5.1 of ISO 28706-3:2017 regarding test water;

---Notes in sections 10.2 and 11.2 of ISO 28706-3:2017 have been removed.

Introduction

GB/T 9989 aims to describe the test methods for the chemical resistance of enamel, and is proposed to consist of five parts.

---Part 1: Determination of Acid Resistance at Room Temperature. The purpose is to evaluate the chemical resistance of enamel in an acidic environment at room temperature. It can provide testing methods.

---Part 2: Determination of resistance to chemical corrosion by boiling acids, boiling neutral liquids, alkaline liquids and their vapors. The purpose is to evaluate the resistance of enamel.

This study investigates the corrosion resistance of ceramics under high temperatures and in the presence of liquids and vapors with different chemical properties, and provides testing methods.

---Part 3: Determination of resistance to chemical attack by alkaline solutions using hexagonal or square glass containers. The purpose is to... The chemical resistance of enamel in alkaline solution environments in containers of specific shapes is evaluated and a test method is provided.

---Part 4: Determination of resistance to alkaline solutions using cylindrical containers. The purpose is to utilize cylindrical containers to determine resistance to alkaline solutions.

The liquid erosion test method is mainly applicable to chemical enamel.

---Part 5: Determination of chemical resistance in enclosed systems. The purpose is to assess the performance of enamel used in chemical processing. The evaluation provides testing methods.

The erosion of enamel and porcelain enamel by aqueous solutions is a hydrolytic process. The main component of the enamel layer is silicon dioxide, which is a three-dimensional silicon dioxide.

The acid-silicone network structure, after hydrolysis, forms silicate or silicate acid that dissolves into the etching medium. Other components (mainly metal oxides) also... It will hydrolyze, forming corresponding metal hydroxide ions or hydroxides. All the products of corrosion will dissolve to some extent into the corrosive medium.

The entire erosion process results in a loss of weight per unit area of the material.

The amount of erosion on enamel surfaces is related to the erosion time; some aqueous solutions show a linear relationship, while others show a logarithmic relationship.

Only when the erosion of an aqueous solution exhibits a linear relationship can the rate of weight loss per unit area [g/(m2.h)] be accurately calculated using scientific methods. and erosion rate (mm/a).

The key factors influencing the corrosion of enamel surfaces by aqueous solutions are the quality of the enamel, temperature, and pH. The limited solubility of silica also... It plays a certain role in inhibiting corrosion. The following lists the corrosion of different types of enamel under different corrosion conditions.

a) At 80°C, alkaline solutions (such as 0.1 mol/L sodium hydroxide, see Chapter 9 of ISO 28706-4:2016) affect the silicate composition of enamel.

Network erosion is quite significant; silicates and most other hydrolyzed components dissolve in the alkaline solution, and the amount of erosion increases proportionally with the test time.

Linear relationship. Therefore, the experimental results can be expressed as the rate of weight loss per unit area (weight loss per unit area and per unit time) and the erosion rate. It is expressed as a rate (mm/a).

b) At room temperature, weak acid solutions (such as citric acid, see Chapter 9 of GB/T 9989.1-2015) or strong acid solutions (such as sulfuric acid, see Chapter 9 of GB/T 9989.1-2015)

GB/T 9989.1-2015, Chapter 10, shows minimal erosion of the silicate network in enamel, but other surface components exhibit a certain degree of precipitation.

The test revealed that high-acid-resistant enamel showed no significant changes on its surface. However, enamel with poor acid resistance showed... The surface will show signs of erosion or become rough.

c) In boiling acidic solutions (see GB/T 9989.2-2025), the silicate network of the enamel layer was eroded, and silica and Other enamel components will dissolve in the solution; however, silica has low solubility in acidic solutions, and the dissolved silica... It quickly reaches saturation in the etching solution, and etched deposits only appear on the enamel surface. Acid etching will be inhibited, and the etching rate will significantly decrease. The decline is evident.

Note: Glass testing apparatus will precipitate silicon dioxide under acid corrosion, which also has a certain inhibitory effect on the corrosion of enamel layer.

In the gas phase test, the condensate formed on the sample surface contained no dissolved enamel components, effectively preventing this type of corrosion. Its function.

The following are examples of nonlinear erosion [see 1)] and linear erosion [see 2)] in enamel.

1) Boiling citric acid (see Chapter 11 of GB/T 9989.2-2025) and 30% boiling sulfuric acid (see GB/T 9989.2-2025)

Chapter 12 Because the gas phase contains only trace amounts of acid, liquid phase tests are usually performed only. Acid corrosion is not only inhibited... The impact is significant, and the amount of erosion depends on the duration of the experiment. Therefore, the experimental results are expressed as weight loss per unit area and cannot be accounted for. Calculate the rate of weight loss per unit area.

2) 20% boiling hydrochloric acid (see Chapter 13 of GB/T 9989.2-2025)

Since hydrochloric acid is an azeotropic acid, its concentration is the same in both the liquid and gas phases, so liquid phase testing is not required.

Violent boiling prevented the agglomerates from exerting an inhibitory effect, and the erosion rate showed a linear relationship with the test time. Therefore, the test results... The results can be expressed as the rate of weight loss per unit area (weight loss per unit area and per unit time) and the erosion rate (mm/a).

d) In the liquid phase test conducted under high temperature and high pressure conditions (see GB/T 9989.5-2015), the corrosion of enamel by acidic solution is... The reaction was severe. To avoid any inhibitory effect, the test time was limited to 24 hours, and the proportion of acid etching on the enamel surface was relatively high.

(Simulating conditions within a chemical reaction vessel). The amount of erosion is linearly related to the time of the experiment. Therefore, 20% hydrochloric acid (see...)

GB/T 9989.5-2015 Chapter 8), simulated solutions (see GB/T 9989.5-2015 Chapter 10) or process fluids (see The test results of GB/T 9989.5-2015, Chapter 11, can be expressed as the rate of weight loss per unit area (per unit area and per unit time). It is expressed as weightlessness.

e) In boiling water (see Chapter 14 of GB/T 9989.2-2025), the silicate network is very stable. Enamel surfaces are mainly characterized by infiltration.

Primarily transparent, the solubility of silica is very limited. In the liquid phase, highly corrosion-resistant enamels exhibit strong corrosion resistance.

Vapor phase erosion can be used to describe similar erosion. However, if the enamel tested has poor chemical stability, alkali gold may precipitate on the enamel surface.

Metallic ions can increase the pH of a solution and increase the corrosive effect of the liquid phase. Therefore, useful information can be obtained from both the liquid and gas phases.

f) Because it is impossible to determine whether the erosion is linear or nonlinear, the experimental results can only be expressed as weight loss per unit area, and the experimental results should be provided. Verification time.

g) For standard solutions tested at 24h or 168h (see Chapter 10), because it cannot be determined whether the erosion curve is linear... Because it is a biological process, the calculation of the erosion rate is not included in the test report.

h) For other acidic solutions (see Chapter 16 of GB/T 9989.2-2025) and other alkaline solutions (see Chapter 11 and see...)

ISO 28706-4:2016 Chapter 11), because it is uncertain whether the erosion rate is linear during the test, therefore, in the test report... The report does not include calculations of the erosion rate.

The test parameters (medium, temperature, and time) in this document are not applicable to enamel materials fired below 700°C.

(For example, aluminum enamel) other media, temperatures, and/or times should be used. These tests can be performed according to Parts 1 to 4 of GB/T 9989.

The method described in the "Other Test Solutions" section is followed.

Warning: Those using this document should have formal laboratory work experience. This document does not address all possible safety issues.

Users are responsible for taking appropriate safety and health measures and ensuring compliance with relevant national laws and regulations.

1 Scope

This document describes a test method for determining the resistance of enamelware to chemical attack by alkaline solutions using hexagonal or quadrangular glass containers.

This document is applicable to testing the resistance of enamel products and porcelain enamel coatings to chemical erosion by alkaline solutions.

2 Normative references

The contents of the following documents, through normative references within the text, constitute essential provisions of this document. Dated citations are not included.

For references to documents, only the version corresponding to that date applies to this document; for undated references, the latest version (including all amendments) applies. This document.

GB/T 6031 Determination of hardness of vulcanized rubber or thermoplastic rubber (10IRHD~100IRHD) (GB/T 6031-2017, ISO 48:2010, IDT)

GB/T 6682 Specifications and test methods for water used in analytical laboratories (GB/T 6682-2008, ISO 3696:1987, MOD)

GB/T 28212 Condensers for Laboratory Glassware (GB/T 28212-2011, ISO 4799:1978, NEQ)

GB/T 34843 3.3 Properties of Borosilicate Glass (GB/T 34843-2017, ISO 3585:1998, MOD)

GB/T 38166 Preparation of specimens for steel plate enamel, aluminum enamel and cast iron enamel (GB/T 38166-2019, ISO 28764:2015, MOD)

3 Terms and Definitions

This document does not contain any terms or definitions that need to be defined.

4 Principles

Under specified temperature and time conditions, the enamel layer was subjected to erosion by an alkaline solution. Its weight loss was measured and the rate of weight loss per unit area was calculated.

5 Reagents

All reagents used in the experiment were of analytical grade (unless otherwise specified).

5.1 Test water. meets the requirements of Grade 3 water in GB/T 6682.

5.2 Degreasing agents. used for cleaning test equipment and samples, such as ethanol or test water containing a few drops of detergent (5.1).

5.3 Sodium triphosphate (Na5P3O10).

5.4 Anhydrous sodium carbonate (Na2CO3).