JPH02122248A - Detecting method for deterioration of coating film of coated metallic member - Google Patents
Detecting method for deterioration of coating film of coated metallic memberInfo
- Publication number
- JPH02122248A JPH02122248A JP27712688A JP27712688A JPH02122248A JP H02122248 A JPH02122248 A JP H02122248A JP 27712688 A JP27712688 A JP 27712688A JP 27712688 A JP27712688 A JP 27712688A JP H02122248 A JPH02122248 A JP H02122248A
- Authority
- JP
- Japan
- Prior art keywords
- coating film
- paint film
- deterioration
- degree
- painted metal
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 230000006866 deterioration Effects 0.000 title claims abstract description 26
- 238000000034 method Methods 0.000 title claims description 24
- 239000011248 coating agent Substances 0.000 title abstract description 44
- 238000000576 coating method Methods 0.000 title abstract description 44
- 239000003973 paint Substances 0.000 claims abstract description 62
- 239000002184 metal Substances 0.000 claims description 50
- 239000008151 electrolyte solution Substances 0.000 claims description 18
- 230000007547 defect Effects 0.000 claims description 17
- 239000003792 electrolyte Substances 0.000 abstract description 9
- 230000002950 deficient Effects 0.000 abstract description 5
- 239000000523 sample Substances 0.000 description 11
- 238000001514 detection method Methods 0.000 description 5
- 229910001335 Galvanized steel Inorganic materials 0.000 description 4
- 239000008397 galvanized steel Substances 0.000 description 4
- 238000005259 measurement Methods 0.000 description 4
- 238000007796 conventional method Methods 0.000 description 3
- 230000007797 corrosion Effects 0.000 description 3
- 238000005260 corrosion Methods 0.000 description 3
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000005611 electricity Effects 0.000 description 2
- 238000002847 impedance measurement Methods 0.000 description 2
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 230000002265 prevention Effects 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- 239000007921 spray Substances 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 239000004593 Epoxy Substances 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 238000005536 corrosion prevention Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005868 electrolysis reaction Methods 0.000 description 1
- 238000011158 quantitative evaluation Methods 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
Landscapes
- Testing Resistance To Weather, Investigating Materials By Mechanical Methods (AREA)
- Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
Abstract
Description
（産業上の利用分野）
この発明は、塗膜を有する塗装金属部材、例えば自動車
のボディ外板において、ピンホール等の塗膜欠陥部分や
塗膜はく離部分の発生による塗膜の劣化の程度を検出し
てその防錆能力を評価するのに利用される塗装金属部材
の塗膜劣化度検出方法に関するものである。
（従来の技術）
塗装金属部材の塗膜の劣化度を検出してその防錆能力を
評価するのに利用される従来の方法としては、例えば、
コロ−ジョンレートメータ法、タンジェストデルタ法、
インピーダンス測定法などがある。
これらのうち、コロ−ジョンレートメータ法は、第５図
に示すように、金属板３１の表面に塗膜３２を形成させ
た塗装金属部材３３の塗膜防錆能力を評価するに際し、
塗装金属部材３３の塗膜３２に、容器３４内に収容した
電解液３５を接触させた状態とし、電解液３５中に基準
極３６と対極３７とを設け、基準極（Ｒ） ３６と対極
（Ｃ）３７と塗装金属部材（Ｗ）３３との間にメインユ
ニット３８より通電して塗装金属部材３３を分極させ、
・、このときに流れる電流や一定時間に流れる電気量を
測定することによって、塗膜３２の劣化度を推定する方
法である。
また、タンジェントデルタ法は、電解液に浸漬させた対
極と前記電解液と接触させた状態の塗装金属部材との間
に例えば４００Ｈｚ程度の交流を印加してそのときの位
相差のタンジェントを測定することにより塗膜の劣化の
程度を推定する方法である。
さらに、インピーダンス法は、塗装金属部材に電解液を
接触させた状態にして、前記電解液に浸漬した電極と塗
装金属部材との間に広い周波教範、囲で交流を印加し、
位相が４５°となる周波数の値によって塗膜のはく離の
程度を測定し、この周波数の値がはく離面積に比例する
ものとしてはく離の量を推定する方法である（「防食技
術」Ｖｏｕ、３６．Ｎｏ、３．１９８７ 第１３４頁
〜１４１頁）。
（発明が解決しようとする課題）
しかしながら、このような従来の塗装金属部材の塗膜劣
化度検出方法において、前二者のコロ−ジョンレートメ
ータ法、およびタンジェントデルタ法では、塗装金属部
材が電解液と接触している状態において等価な電気回路
についての考察がなされておらず、単なる経験により得
られた方法に従って塗装金属部材の塗膜の劣化を評価す
るようにしていたため、塗膜の劣化を定量的に評価する
ことができないという課題を有していた。
また、後者のインピーダンス測定法では、塗装金属部材
の塗膜のはく離面積を定量的に評価することが可能であ
るものの、塗膜にピンホール等の塗膜欠陥部分がある場
合には測定に誤差を生じゃすく、塗膜の劣化を正しく評
価することができないことがあるという課題があった。
（発明の目的）
この発明は、上述した従来の課題にかんがみてなされた
もので、塗膜を有する塗装金属部材において、ピンホー
ル等の塗膜欠陥部分や塗膜はく離部分を生じて劣化した
塗膜について、ピンホール等の塗膜欠陥部分の面積およ
び塗膜はく離部分の面積を別々にそして各々定量的に検
出して、塗膜の劣化度合を定量的に評価することが可能
である塗装金属部材の塗膜劣化度検出方法を提供するこ
とを目的としている。(Industrial Application Field) This invention aims to reduce the degree of deterioration of the paint film due to the occurrence of paint film defects such as pinholes and peeling parts in painted metal parts having a paint film, such as the outer panel of the body of an automobile. The present invention relates to a method for detecting the degree of paint film deterioration of a painted metal member, which is used to detect and evaluate the rust prevention ability. (Prior Art) Conventional methods used to detect the degree of deterioration of the coating film of painted metal members and evaluate its rust prevention ability include, for example,
Corrosion rate meter method, tangest delta method,
Examples include impedance measurement methods. Among these, the corrosion rate meter method, as shown in FIG.
The coating film 32 of the painted metal member 33 is brought into contact with the electrolytic solution 35 housed in the container 34, a reference electrode 36 and a counter electrode 37 are provided in the electrolytic solution 35, and the reference electrode (R) 36 and the counter electrode ( C) Applying electricity from the main unit 38 between 37 and the painted metal member (W) 33 to polarize the painted metal member 33,
- This is a method of estimating the degree of deterioration of the coating film 32 by measuring the current flowing at this time or the amount of electricity flowing over a certain period of time. Furthermore, in the tangent-delta method, an alternating current of, for example, about 400 Hz is applied between a counter electrode immersed in an electrolytic solution and a painted metal member in contact with the electrolytic solution, and the tangent of the phase difference at that time is measured. This is a method for estimating the degree of deterioration of the paint film. Furthermore, in the impedance method, an electrolytic solution is brought into contact with the painted metal member, and an alternating current is applied in a wide frequency range between the electrode immersed in the electrolyte and the painted metal member,
This method measures the degree of peeling of the coating film based on the value of the frequency at which the phase is 45°, and estimates the amount of peeling based on the assumption that this frequency value is proportional to the peeled area ("Corrosion Prevention Technology" Vou, 36. No. 3.1987, pp. 134-141). (Problem to be Solved by the Invention) However, in such conventional methods for detecting the degree of paint film deterioration of painted metal members, in the former two corrosion rate meter methods and tangent delta methods, the painted metal members are exposed to electrolysis. No consideration was given to the equivalent electrical circuit in the state of contact with liquid, and the deterioration of the paint film of painted metal parts was evaluated based on a method obtained simply from experience. The problem was that quantitative evaluation was not possible. In addition, although the latter impedance measurement method makes it possible to quantitatively evaluate the peeling area of the paint film on painted metal parts, errors may occur in the measurement if there are paint film defects such as pinholes in the paint film. However, there was a problem in that it was sometimes impossible to accurately evaluate the deterioration of the paint film. (Purpose of the Invention) This invention has been made in view of the above-mentioned conventional problems, and it is a painted metal member having a coating film that has deteriorated due to defects in the coating film such as pinholes or peeling parts. It is possible to quantitatively evaluate the degree of deterioration of a paint film by separately and quantitatively detecting the area of paint film defects such as pinholes and the area of peeling parts of the paint film. The purpose of this invention is to provide a method for detecting the degree of paint film deterioration of a member.
この発明は、塗膜を有する塗装金属部材のピンホール等
の塗膜欠陥部分や塗膜はく離部分の発生による塗膜の劣
化度を検出するに際し、塗装金属部材の塗膜表面に電解
液を接触させた状態にして、前記電解液に接する電極と
前記塗装金属部材との間に所定の間隔で周波数を変化さ
せた交流電圧を印加し、前記交流電圧の印加により前記
塗装金属部材の電気化学的インピーダンスの周波数変化
を生じさせ、前記電気化学的インピーダンスの周波数変
化における複数の変曲点のうち異なる変曲点によりそれ
ぞれ前記塗膜のピンホール等の塗膜欠陥部分や塗膜はく
離部分の発生度合を別々に検出する構成としたことを特
徴としており、このような塗装金属部材の塗膜劣化度検
出方法の構成を上述した従来の課題を解決するための手
段としており、実施態様においては、電解液に接する電
極と塗装金属部材との間に一定の間隔で周波数を変化さ
せた交流電圧を印加することにより、４つの変曲点をも
つ塗装金属部材の電気化学的インピーダンス変化を前記
交流の周波数変化により発生させ、この４つの変曲点を
もつインピーダンスの周波数変化において第２の変曲点
の値によりピンホール等の塗膜欠陥部分の面積を検出し
、第２の変曲点の値と第４の変曲点の値とにより塗膜は
く離部分の面積を検出するというように、塗膜欠陥部分
の面積と塗膜はく離部分の面積とを並列の検出回路によ
り分離して検出する。
この発明に係る塗装金属部材の塗膜劣化度検出方法の実
施に用いられる検出装置としては、電解液を収容してい
ると共に前記電解液に接する電極をそなえ且つ塗膜を有
する塗装金属部材の前記塗膜に前記電解液の接触を可能
とじたプローブと、前記プローブの電極と前記塗装金属
部材との間に所定の間隔で周波数を変化させた交流電圧
を印加する電源供給手段と、前記プローブの電解液と前
記塗装金属部材の塗膜とが接触した状態で前記プローブ
の電極と前記塗装金属部材との間に前記電源供給手段に
より所定の間隔で周波数を変化させた交流電圧を印加す
ることにより発生する複数の変曲点をもつインピーダン
スの周波数変化を測定して前記複数の変曲点のうち選択
された変曲点により前記塗膜のピンホール等の塗膜欠陥
部分や塗膜はく離部分の発生度合をそれぞれ別々に分離
して検出する検出手段と、を備えた構成のものとするこ
とができる。
（発明の作用）
この発明に係る塗装金属部材の塗膜劣化度検出方法では
、上記の構成を有しているものであるから、所定の間隔
で周波数を変化させた交流電圧を印加することにより発
生する複数の変曲点をもつインピータンスを測定して当
該インピーダンスの周波数変化において特定された変曲
点をとらえるようにし、塗装金属部材が電解液と接触し
ている状態で表わされる等価回路においてピンホール等
の塗膜欠陥部分と塗膜はく離部分との並列回路が形成さ
れるようにしているので、塗膜欠陥部分の面積と塗膜は
く離部分の面積とがそれぞれ別々に分離して演算されう
るものとなり、ピンホール等の塗膜欠陥部分および塗膜
はく離部分の発生度合がそれぞれ別々にそして各々定量
的に検出されて、塗装金属部材の塗膜の劣化度合が評価
される。
（実施例）
第１図はこの発明の実施例を示している。
第１図に示すように、塗装金属部材１は、金属板２の例
えば片面に塗膜３を有しているものであり、この塗膜３
側には、電解液４を収容すると共に前記電解液４と接す
る電極５をそなえ且つ前記塗膜３に前記電解液４の接触
を可能とした筒状の容器６をそなえたプローブ７を固定
具８，８により固定してあり、塗膜３と容器５（プロー
ブ７）との間にシールリング９を介在させることによっ
て電解液４の漏れを防ぐようにしている。この場合、電
解液４としては、想定する腐食環境によっても異なるが
、通常の場合、０．５ｍｏｕ／文（約３％）のＮａＣ１
水溶液が用いられる。
このプローブ７の電極５と塗装金属部材１との間には、
それぞれ通電線５ａ、ｌａを介して、定電圧電源１１が
接続してあり、この定電圧電源１１には、任意の周波数
を発生することができる発振器１２が接続してあり、こ
の定電圧電源１１と発振器１２とで電源供給手段１３を
構成している。
この電源供給手段１３の定電圧電源１１および発振器１
２には、前記電源供給手段１３によって所定の間隔で周
波数を変化させた交流電圧を印加させた際に発生する複
数の変曲点をもつインピーダンスの周波数変化を測定し
て前記複数の変曲点により塗膜のピンホール等の塗膜欠
陥部分の面積や塗膜はく離部分の面積をそれぞれ別々に
算出する演算器（ＣＰＵ）１４が接続してあり、こらら
の演算結果は表示器１５で表示されるようにしてあって
、この演算器１４と表示器１５で検出手段１６を構成し
ている。
第２図は塗膜３が劣化していない部分の塗装金属部材１
とプローブ７との当接部分における電気的な等価回路を
示すものであって、Ｒｓｏｌは電解液４の抵抗、Ｃｆは
塗膜３の測定面全体における静電容量、Ｒｆは塗膜３の
抵抗を示している。
また、第３図は塗膜３が劣化している部分の塗装金属部
材１とプローブ７との当接部分における電気的な等価回
路を示すものであって、ＲｓｏＭは電解液４の抵抗、Ｃ
ｆは塗膜３の測定面全体における静電容量、Ｒｆは塗膜
３の抵抗であってはく離面績に反比例する値、Ｃｄｕは
塗膜３のはく離部分における電気二重層容量、Ｒｃは塗
膜３のはく離部分における反応抵抗を示し、この回路に
よって塗膜３のはく離部分の面積を定量的に測定する電
気回路が構成されるようにしている。
また、同じく第３図に示す等価回路において、Ｒ，ｐは
ピンホール内の溶液抵抗、Ｃｄ１ｐはピンホールの底部
における電気二重層容量、Ｒｃｐはピンホールの底部に
おける反応抵抗を示し、この回路によって塗膜３のピン
ホール部分（塗膜欠陥部分）の面積を定量的に測定する
電気回路が構成されるようにしている。
この実施例においては、塗装金属部材１として亜鉛めっ
き鋼板を選び、金属板２（鋼板）の表面に塗膜３として
エポキシを２５１Ｌｍの厚さで塗装した亜鉛めっき鋼板
を塩水噴霧試験に３ケ月供したのち、亜鉛めっき鋼板の
電気化学的インピーダンスを測定した。この結果を第４
図に示す。
第４図において、曲線１は前述した従来のインピーダン
ス法によって評価できるが、曲線２では位相が４５°と
なる周波数が４個所現われるため評価することができな
い。なお、第４図の点線は第３図に示した等価回路を用
いでシミュレートしたものであり、実際の測定結果とよ
く対応している。
そこで、第４図において、曲線２のインピーダンスの変
曲点を高い方からｆｌ 、’ｆ２ 、ｆ３ｆ４とする
と、第３図に示した等価回路について検討した結果、次
のことが判明した。
まず、ｆ２は回路定数と以下に示す関係がある。
ｆ２ ＝−１／（２電ＲｐＣｆ） ・・
・ （１）また、単価面積あたりのＲｐをＲｐｏとし、
ピンホールの面積をＳｌとすると、
ｆ２＝１／（２πＣｆ ＲＰ ’ ／ Ｓ ｓ ）
・・・（２）Ｓ、＝ｆ２Ｘ２πＣｆＲｐ’
・・・（３）１／（２πＲｐ Ｏ／ Ｓ １Ｘ Ｃｄ
立ｐ０ＸＳ＋ ）ｌ／（２πＲｐＯＣｄＪＪｐＯ）
・・・（４）となり、（４）式からｆ３の値は常に
一定であることがわかる。さらに、
Ｃｄ文ｐ＝１／（２πＲＰ’／５ｔｆ３）・・・（５）
ｆ４＝１／（２πＣｄｆＬｐＲ’ ） ・・・（
６）Ｒ’＝１／（２πｆ４Ｃｄ又ｐ） ・・・（７
）ここで、ＲｆＯは単位面積あたりのＲｆであり、Ｓ２
ははく離面績である。
■
したがって、（３）式でＳｌを求めることによりＳ２の
値も決定される。
次に、第４図の曲線２について計算を行うと、
ｆ２ ＝３ ．３Ｘ１０３’ （Ｈｚ）Ｃｆ＝３ ．
９８Ｘ１０−” （Ｆ）Ｒｐ’＝１０（Ω・ ０ｍ２
）
から、（３）式より、
３１ ＝８．３Ｘ １０−４（０ｍ２）０−４（，５Ｘ
ｌＯ’ （Ｈｚ）
であり、（５）式より、
Ｃｄ文ｐ＝＝３．８４ＸＩＯ−８（Ｆ）ｆ４＝１．０Ｘ
１０１
であり、 （７）式より、
Ｒ’＝１．８Ｘ１０Ｓ
ＲｆＯ＝１．３ＸＩＯ５（Ω＊ｃｍ２）Ｒｃｐ’＝１．
６Ｘ１０４ （Ω＊ｃｍ２）であり、（８）式より、
５２＝７．２Ｘ１０’ （０ｍ２）
となる。
したがって、ピンホールの面積は８．３×１０″４ｃｍ
’、はく離面績は７．ＩＸｌＸｌｏｌＣを得ることがで
き、塗膜３の劣化度を検出することが可能である。
なお、定数項であるＲｐ’ 、ＲｆＯ，ＲｃｐＯＣｄｌ
ｐＯ，ＣｆＯの値は被測定系である塗膜の種類に固有の
量であり、あらかじめデータセットとして適切な値を演
算器（ＣＰＵ）１４に入力しておく。This invention involves contacting an electrolytic solution to the surface of the coating film of a painted metal component when detecting the degree of deterioration of the coating film due to the occurrence of coating film defects such as pinholes or peeling of the coating film on the painted metal component. An alternating current voltage whose frequency is varied at a predetermined interval is applied between the electrode in contact with the electrolytic solution and the painted metal member, and the application of the alternating voltage causes electrochemical changes in the painted metal member. A frequency change in the impedance is caused, and different inflection points among a plurality of inflection points in the frequency change in the electrochemical impedance can be used to determine the degree of occurrence of paint film defects such as pinholes in the paint film or peeling parts of the paint film. The structure of the method for detecting the degree of paint film deterioration of painted metal members is a means to solve the above-mentioned conventional problems. By applying an alternating current voltage whose frequency is varied at regular intervals between the electrode in contact with the liquid and the painted metal member, changes in the electrochemical impedance of the painted metal member having four inflection points can be measured by applying the alternating current voltage at the frequency of the alternating current. The area of a paint film defect such as a pinhole is detected based on the value of the second inflection point in the frequency change of the impedance that has four inflection points, and the area of the paint film defect such as a pinhole is detected and The area of the paint film defective portion and the area of the paint film peeled portion are detected separately by parallel detection circuits, such as by detecting the area of the paint film peeling portion based on the value of the fourth inflection point. A detection device used for carrying out the method for detecting the degree of coating film deterioration of a painted metal member according to the present invention contains an electrolytic solution, is provided with an electrode in contact with the electrolytic solution, and has a coating film on the coated metal member. a probe capable of bringing the electrolyte into contact with the coating film; a power supply means for applying an alternating current voltage with a frequency varied at predetermined intervals between the electrode of the probe and the painted metal member; By applying an alternating current voltage whose frequency is varied at predetermined intervals by the power supply means between the electrode of the probe and the coated metal member in a state where the electrolyte and the coating film of the coated metal member are in contact with each other. The frequency change of the impedance having a plurality of inflection points that occurs is measured, and the selected inflection point is used to detect defects in the paint film such as pinholes and peeling parts of the paint film. and detection means for separately detecting the degrees of occurrence. (Operation of the Invention) Since the method for detecting the degree of paint film deterioration of a painted metal member according to the present invention has the above configuration, by applying an alternating current voltage whose frequency is changed at predetermined intervals, The generated impedance with multiple inflection points is measured to capture the specified inflection point in the frequency change of the impedance, and in the equivalent circuit represented when the painted metal member is in contact with the electrolyte. Since a parallel circuit is formed between the paint film defects such as pinholes and the paint film peeling areas, the area of the paint film defects and the area of the paint film peeling are calculated separately. The degree of occurrence of paint film defects such as pinholes and paint film peeling parts is detected separately and quantitatively, and the degree of deterioration of the paint film of the painted metal member is evaluated. (Embodiment) FIG. 1 shows an embodiment of this invention. As shown in FIG. 1, a coated metal member 1 has a coating film 3 on one side of a metal plate 2, for example.
A probe 7 is mounted on the side thereof as a fixture, and is equipped with a cylindrical container 6 that accommodates an electrolytic solution 4 and is provided with an electrode 5 that is in contact with the electrolytic solution 4 and that allows the electrolytic solution 4 to come into contact with the coating film 3. 8, 8, and a seal ring 9 is interposed between the coating film 3 and the container 5 (probe 7) to prevent leakage of the electrolytic solution 4. In this case, the electrolyte 4 is usually 0.5 mou/liter (approximately 3%) of NaCl, although it differs depending on the envisaged corrosive environment.
Aqueous solutions are used. Between the electrode 5 of this probe 7 and the painted metal member 1,
A constant voltage power source 11 is connected to each other via current-carrying lines 5a and la, and an oscillator 12 capable of generating an arbitrary frequency is connected to this constant voltage power source 11. and the oscillator 12 constitute a power supply means 13. Constant voltage power supply 11 and oscillator 1 of this power supply means 13
2, measuring the frequency change of impedance having a plurality of inflection points that occurs when the power supply means 13 applies an AC voltage whose frequency is changed at predetermined intervals, and determining the plurality of inflection points. A computing unit (CPU) 14 is connected to the unit which separately calculates the area of paint film defects such as pinholes in the paint film and the area of peeling parts of the paint film, and these calculation results are displayed on a display 15. The arithmetic unit 14 and the display 15 constitute a detection means 16. Figure 2 shows a part of the painted metal member 1 where the coating film 3 has not deteriorated.
and the probe 7, Rsol is the resistance of the electrolytic solution 4, Cf is the capacitance of the entire measurement surface of the coating film 3, and Rf is the resistance of the coating film 3. It shows. Further, FIG. 3 shows an electrical equivalent circuit at the contact area between the coated metal member 1 and the probe 7 where the coating film 3 has deteriorated, where RsoM is the resistance of the electrolytic solution 4, and C
f is the capacitance of the entire measurement surface of the coating film 3, Rf is the resistance of the coating film 3 and is inversely proportional to the peeling surface resistance, Cdu is the electric double layer capacitance at the peeled part of the coating film 3, and Rc is the coating film 3 shows the reaction resistance at the peeled part of the coating film 3, and this circuit constitutes an electric circuit for quantitatively measuring the area of the peeled part of the coating film 3. Also, in the equivalent circuit shown in Figure 3, R and p represent the solution resistance inside the pinhole, Cd1p represents the electric double layer capacitance at the bottom of the pinhole, and Rcp represents the reaction resistance at the bottom of the pinhole. An electric circuit is configured to quantitatively measure the area of the pinhole portion (defected portion of the coating film) of the coating film 3. In this example, a galvanized steel plate was selected as the painted metal member 1, and the galvanized steel plate was coated with epoxy to a thickness of 251 Lm as the coating film 3 on the surface of the metal plate 2 (steel plate) and was subjected to a salt spray test for 3 months. After that, the electrochemical impedance of the galvanized steel sheet was measured. This result is the fourth
As shown in the figure. In FIG. 4, curve 1 can be evaluated by the conventional impedance method described above, but curve 2 cannot be evaluated because four frequencies with a phase of 45° appear. Note that the dotted line in FIG. 4 is simulated using the equivalent circuit shown in FIG. 3, and corresponds well to the actual measurement results. Therefore, in FIG. 4, assuming that the inflection points of the impedance of curve 2 are fl, 'f2, and f3f4 in descending order, the following was found as a result of examining the equivalent circuit shown in FIG. First, f2 has the following relationship with a circuit constant. f2 = -1/(2 electric RpCf) ・・
・ (1) Also, let Rp per unit price area be Rpo,
If the area of the pinhole is Sl, then f2=1/(2πCf RP'/S s )
...(2) S, = f2X2πCfRp'
...(3) 1/(2πRp O/ S 1X Cd
Standing p0XS+ )l/(2πRpOCdJJpO)
...(4), and it can be seen from equation (4) that the value of f3 is always constant. Furthermore, Cd sentence p=1/(2πRP'/5tf3)...(5)
f4=1/(2πCdfLpR') ...(
6) R'=1/(2πf4Cd or p)...(7
) Here, RfO is Rf per unit area, and S2
It is a peeling grade. (2) Therefore, the value of S2 is also determined by finding Sl using equation (3). Next, when calculating curve 2 in FIG. 4, f2 = 3. 3X103' (Hz)Cf=3.
98X10-” (F)Rp'=10(Ω・0m2
) From equation (3), 31 = 8.3X 10-4(0m2)0-4(,5X
lO' (Hz), and from equation (5), Cd sentence p = = 3.84XIO-8 (F) f4 = 1.0X
101, and from equation (7), R'=1.8X10S RfO=1.3XIO5(Ω*cm2)Rcp'=1.
6X104 (Ω*cm2), and from equation (8), 52=7.2X10' (0m2). Therefore, the area of the pinhole is 8.3 x 10″4cm
', peeling surface score was 7. IXlXlolC can be obtained, and the degree of deterioration of the coating film 3 can be detected. Note that the constant terms Rp', RfO, RcpOCdl
The values of pO and CfO are quantities specific to the type of coating film that is the system to be measured, and appropriate values are input into the computing unit (CPU) 14 in advance as a data set.
この発明に係る塗装金属部材の塗膜劣化度検出方法では
、塗装金属部材の塗膜表面に電解液を接触させた状態に
して、前記電解液に接する電極と前記塗装金属部材との
間に所定の間隔で周波数を変化させた交流電圧を印加し
、前記交流電圧の印加により前記塗装金属部材の電気化
学的インピーダンスの周波数変化を生じさせ、前記電気
化学的インピーダンスの周波数変化における複数の変曲
点のうち異なる変曲点によりそれぞれ前記塗膜のピンホ
ール等の塗膜欠陥部分や塗膜はく離部分の発生度合を別
々に検出するようにしたから、ピンホール等の塗膜欠陥
部分と塗膜はく離部分の両方を有する劣化した塗膜をも
つ塗装金属部材において、塗膜欠陥部分の面積と塗膜は
く離部分の面積の両方を別々にそして各々定量的に検出
して、塗膜の劣化度合を定量的に評価することが可能で
あるという著しく優れた効果がもたらされる。In the method for detecting the degree of paint film deterioration of a painted metal member according to the present invention, an electrolytic solution is brought into contact with the paint film surface of the painted metal member, and a predetermined distance is set between an electrode in contact with the electrolyte and the painted metal member. applying an alternating voltage whose frequency is changed at an interval of Since the degree of occurrence of paint film defects such as pinholes and paint film peeling is detected separately using different inflection points, the occurrence of paint film defects such as pinholes and paint film peeling can be detected separately. In a painted metal member with a deteriorated paint film that has both parts, the area of the defective part of the paint film and the area of the peeled part of the paint film are detected separately and quantitatively to quantify the degree of deterioration of the paint film. This brings about the remarkable effect that it is possible to evaluate the results visually.
第１図はこの発明に係る塗装金属部材の塗膜劣化度検出
方法の実施例を示す要部説明図、第２図は塗膜が劣化し
ていない部分の塗装金属部材とプローブとの当接部分に
おける電気的な等価回路を示す説明図、第３図は塗膜が
劣化している部分の塗装金属部材とプローブとの当接部
分における電気的な等価回路を示す説明図、第４図は亜
鉛めっき鋼板の塩水噴霧試験後における電気化学的イン
ピーダンスの周波数による変化を測定した結果を示すグ
ラフ、第５図は従来の塗装金属部材の塗膜劣化度検出方
法のうちのインピーダンス法の要部構成を示す説明図で
ある。
１・・・塗装金属部材、
３・・・塗膜、
４・・・電解液、
５・・・
電極、
７・・・プローブ、
３・・・電源供給段、
６・・・
検出手段。Fig. 1 is an explanatory view of the main parts showing an embodiment of the method for detecting the degree of paint film deterioration of a painted metal member according to the present invention, and Fig. 2 shows the contact between the painted metal member and the probe where the paint film has not deteriorated. Figure 3 is an explanatory diagram showing the electrical equivalent circuit at the part where the paint film has deteriorated and where the probe contacts the painted metal member. A graph showing the results of measuring changes in electrochemical impedance due to frequency after a salt spray test on galvanized steel sheets. Figure 5 shows the main structure of the impedance method, which is a conventional method for detecting the degree of paint film deterioration on painted metal parts. FIG. DESCRIPTION OF SYMBOLS 1... Painted metal member, 3... Paint film, 4... Electrolyte, 5... Electrode, 7... Probe, 3... Power supply stage, 6... Detection means.
Claims (1)
欠陥部分や塗膜はく離部分の発生による塗膜の劣化度を
検出するに際し、塗装金属部材の塗膜表面に電解液を接
触させた状態にして、前記電解液に接する電極と前記塗
装金属部材との間に所定の間隔で周波数を変化させた交
流電圧を印加し、前記交流電圧の印加により前記塗装金
属部材の電気化学的インピーダンスの周波数変化を生じ
させ、前記電気化学的インピーダンスの周波数変化にお
ける複数の変曲点のうち異なる変曲点によりそれぞれ前
記塗膜のピンホール等の塗膜欠陥部分や塗膜はく離部分
の発生度合を別々に検出することを特徴とする塗装金属
部材の塗膜劣化度検出方法。(1) When detecting the degree of deterioration of a paint film due to the occurrence of paint film defects such as pinholes or peeling parts of a painted metal member having a paint film, an electrolytic solution is brought into contact with the paint film surface of the painted metal member. an alternating current voltage whose frequency is varied at a predetermined interval is applied between the electrode in contact with the electrolytic solution and the painted metal member, and the application of the alternating voltage changes the electrochemical impedance of the painted metal member. The degree of occurrence of paint film defects such as pinholes in the paint film and paint film peeling parts is determined by different inflection points among the plurality of inflection points in the frequency change of the electrochemical impedance. A method for detecting the degree of paint film deterioration of painted metal members, characterized in that the degree of deterioration of a paint film is detected separately.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63277126A JP2519786B2 (en) | 1988-11-01 | 1988-11-01 | Method for detecting the degree of coating film deterioration of painted metal parts |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63277126A JP2519786B2 (en) | 1988-11-01 | 1988-11-01 | Method for detecting the degree of coating film deterioration of painted metal parts |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH02122248A true JPH02122248A (en) | 1990-05-09 |
| JP2519786B2 JP2519786B2 (en) | 1996-07-31 |
Family
ID=17579156
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP63277126A Expired - Lifetime JP2519786B2 (en) | 1988-11-01 | 1988-11-01 | Method for detecting the degree of coating film deterioration of painted metal parts |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2519786B2 (en) |
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- 1988-11-01 JP JP63277126A patent/JP2519786B2/en not_active Expired - Lifetime
Non-Patent Citations (1)
| Title |
|---|
| PROC OF SYMPOSIUM ON CORROSION PROTECTION BY ORGANIC COATINGS=1987 * |
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|---|---|
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