1、ASD STANDARD NORME ASD ASD NORM prEN 4171 Edition P1 November 2005 PUBLISHED BY THE AEROSPACE AND DEFENSE INDUSTRIES ASSOCIATION OF EUROPE - STANDARDIZATIONGulledelle 94 - B-1200 Brussels - Tel. + 32 2 775 8126 - Fax. + 32 2 763 3565 - www.asd-stan.orgICS: Descriptors: ENGLISH VERSION Aerospace seri
2、es Paints and varnishes Test method for determination of phosphoric acid index Srie arospatiale Peintures et vernis Dtermination de la teneur en acide phosphorique Luft- und Raumfahrt Anstrichstoffe Phosphorsauere Belastung This “Aerospace Series“ Prestandard has been drawn up under the responsibili
3、ty of ASD-STAN (The Aerospace and Defense Industries Association of Europe - Standardization). It is published for the needs of the European Aerospace Industry. It has been technically approved by the experts of the concerned Domain following member comments. Subsequent to the publication of this Pr
4、estandard, the technical content shall not be changed to an extent that interchangeability is affected, physically or functionally, without re-identification of the standard. After examination and review by users and formal agreement of ASD-STAN, it will be submitted as a draft European Standard (pr
5、EN) to CEN (European Committee for Standardization) for formal vote and transformation to full European Standard (EN). The CEN national members have then to implement the EN at national level by giving the EN the status of a national standard and by withdrawing any national standards conflicting wit
6、h the EN. Edition approved for publication 30 November 2005 Comments should be sent within six months after the date of publication to ASD-STAN Non-metallic Material Domain Copyright 2005 by ASD-STAN prEN 4171:20052 Contents Page Foreword2 1 Scope 3 2 Normative references 3 3 Terms and definitions .
7、3 4 Principle3 5 Apparatus .3 6 Specimen4 7 Procedure .4 8 Results5 9 Designation 5 10 Test report 5 Foreword This standard was reviewed by the Domain Technical Coordinator of ASD-STANs Non-metallic Material Domain. After inquiries and votes carried out in accordance with the rules of ASD-STAN defin
8、ed in ASD-STANs General Process Manual, this standard has received approval for Publication. prEN 4171:2005 3 1 Scope This test standard specifies a method for the titration and determination of the phosphoric acid content of an hydroalcoholic solution for aerospace applications. This test method is
9、 relevant for the determination of total acidity and phosphoric acid content in a reactive thinner of a wash primer or in metal cleaners. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited app
10、lies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 1513, Paints and varnishes Examination and preparation of samples for testing. ISO 3696, Water for analytical laboratory use Specification and test methods. ISO 15528, Paints, varnishe
11、s and raw materials for paints and varnishes Sampling. 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 reactive thinner alcoholic phosphoric acid solution, which reacts with the metallic substrate and the base 3.2 metal cleaner aqueous phosph
12、oric acid solution for the removal of slightly oxidic films on aluminium 4 Principle The phosphoric acid content is determined by titration with aqueous solution of sodium or potassium hydroxide after ionisation of the phosphoric acid. Successive pH jumps allow the determination of: total acidity; p
13、hosphoric acid content. 5 Apparatus conical flasks: 250 ml; burette: 50 ml or 100 ml; PTFE coated magnetic stirrer; pipette: 10 ml; prEN 4171:2005 4 buffered solutions (pH = 4,5 and pH = 6,2); indicator solution (helianthine and phenolphtalein); automatic acid/base titrator or glass electrode (and S
14、CE electrode); 1 N sodium or potassium hydroxide solution: (calibrate N using phthalic acid). All chemicals are analytical reagent grade. Titration has to be carried out accordingly. 6 Specimen Test specimen shall be taken directly from the original container. See ISO 1513 and ISO 15528. 7 Procedure
15、 In the conical flask containing an accurate volume of 10 ml, (Vs), of the test specimen, add approximately 150 ml of fresh distilled water in accordance with ISO 3696; Introduce the magnetic stirring bar and pu t the erlenmeyer on the magnetic stirrer; Add few drops of both coloured indicators in c
16、ase of manual procedure; Introduce the glass electrode and the SCE in case of pH-f (V) procedure; Using automatic or manual procedure add slowly the alkaline solution and record alkaline solution volume versus pH or colour change; Determine accurately the volume of alkali added to achieve the first
17、and second end points indicated by observed jumps in pH using the potentiometric method or colour change in the case of the manual procedure. According to the pKa of the phosphoric acid (2,1, 7,2, 12,7) three main pH jumps are theoretically detected, but the two first jumps (pH 4,5 and 9) are detect
18、ed with good accuracy (see Figure 1); Note V1 and V2, the alkaline solution volume required to obtain these two pH jumps or colour change. 9 4,5 V (ml) Figure 1 Titration of phosphoric acid by a strong base. Typical curve CAUTION In case of solution containing phosphoric acid as only acidic material
19、, theoretically V1 = V2 but due to carbonic acid dissolved in water V2 may be slightly higher than V1. prEN 4171:2005 5 8 Results Acid normality: N1 = (V1*N)/Vs. H3PO4content: Na = 3*(V2-V1)*N/Vs. In order to avoid the contribution of the presence of any other strong acid in the test specimen, for t
20、he calculation of the phosphoric acid content only the difference (V2 V1) shall be used. 9 Designation EXAMPLE Description block PHOSPHORIC ACID INDEX Identity block EN4171 Number of this standard 10 Test report This test standard specifies a method for the titration and determination of the phospho
21、ric acid content of an hydroalcoholic solution used in etch primer activators for aerospace applications. a) designation of standard; b) date; c) product designation; d) batch number; e) code number; f) N (Normality of sodium or potassium hydroxide solution); g) N1 (Acid normality); h) Na (H3PO4content); i) test procedure: coloured indicators, pH = f (V).
