JPH0668160B2 - Monitoring method for electrodeposition coating of cylindrical tank - Google Patents

Description

The present invention relates to an electrodeposition coating monitoring method for a cylindrical tank.

[Conventional technology]

A cylindrical tank, as shown in the vertical sectional view of FIG.
To coat the inner surface of a tank whose interior is partitioned into two or three chambers via a partition wall and only the small diameter mouthpiece is installed on the side wall, conventional spray coating is practically used in addition to spray coating. There is no suitable means.

Here, 2 is a small-diameter screw cap for connecting a pipe, a safety valve, a drain valve, etc., which are respectively provided at the center of the end plate and the cylindrical portion.

[Problems to be Solved by the Invention]

However, spray coating has the following problems.

(1) The spray nozzle cannot be inserted unless the inner diameter of the mouthpiece is quite large.

(2) There is no suitable means to inspect whether the thickness of the coating film is uniform.

(3) Since it is difficult to spray coat the entire inner surface with a uniform thickness, the thickness of the coating film varies, and several years later, corrosion starts locally from the thin portion of the coating film.

The present invention has been proposed in view of such circumstances, and provides an economical electrodeposition coating monitoring method for a cylindrical tank, which coats the inner surface and / or the outer surface with a uniform thickness quickly and reliably by electrodeposition coating. The purpose is to provide.

[Means for Solving the Problems]

To this end, the present invention inserts a rod-shaped electrode through an insulating bush on the central axis of a cylindrical tank whose both ends are closed by end plates and / or arranges a plate-shaped electrode facing the outside of the tank, Is filled with an electrodeposition coating liquid, the above electrode is used as a positive electrode, the above tank is used as a negative electrode, and a DC voltage is applied between them to perform electrodeposition coating on the inner surface and / or outer surface of the tank. After determining the reference current curve as a reference by measuring the electrodeposition coating current flowing through the electrode and tank that changes with time, based on the above reference current curve, the coating on the tank is normally performed when a predetermined time has elapsed from the start of coating. The reference current value having an allowable range is set in advance, and when the tank is subsequently electrodeposited, the electrodeposition coating current value flowing through the electrode and the tank when the predetermined time has elapsed is detected. To, normal or electrodeposition coating according to whether the detected value is within the allowable range of the reference current value
Characterized by determining an abnormality.

[Action]

With such a configuration, when the tank is filled with the electrodeposition coating liquid and a predetermined voltage is applied between the electrode and the tank to perform electrodeposition coating, contact failure, insulation failure of the entire circuit including the electrode, It is possible to quickly detect the presence or absence of disconnection, etc., and monitor whether or not uniform, smooth and strong inner surface and / or outer surface coating is being performed with a specified current.

〔Example〕

An embodiment in which the present invention is applied to a one-chamber type air tank will be described with reference to the drawings. FIG. 1 is a side view showing a tank in an electrodeposition coating bath, and FIG. 2 is a portion showing a supporting portion of the tank shown in FIG. FIG. 3 is a side view, FIG. 3 is a partially enlarged sectional view showing the bearing of FIG. 2, FIG. 4 is a perspective view and a front view showing the pivoting point of the tank of FIG. 1, and FIG. FIG. 6 is a side view showing a procedure for electrodeposition coating and water rinsing / dehydration of the intermediate chamber of the three-chamber air tank.

First, in FIGS. 1 to 3, the same reference numerals as in FIG. 7 denote the same members as in FIG. 7, and 1 denotes a horizontal cylindrical air tank (hereinafter referred to as a tank). Each of the bases 2 is projectingly provided on the central axis. Reference numeral 3 denotes an insulating bush screwed into each of the bases 2. The insulating bush 3 is made of a metal bush whose entire circumference is covered with an insulating film. The head is coaxial with a non-conductive hollow shaft made of synthetic resin. 4 is projected.

Reference numeral 6 denotes a hollow rod-shaped electrode (hereinafter referred to as an electrode) made of a stainless pipe inserted through the hollow shaft 4, the insulating bush 3 and the center hole of the base 2. Stainless steel is exposed at a portion extending into the tank, and this portion is exposed at this portion. A plurality of nozzle holes 7 are bored in the radial direction and the diagonal axis direction, and the portion other than the exposed portion where the electrodeposition coating solution is dipped is covered with an insulating film 8.

Reference numerals 9 and 9 denote a pair of nylon bearings in which inner races are fitted to the hollow shafts 4 and 4, respectively, and the outer races of the bearings 9 are the lower ends of a pair of support angles 10 and 10 vertically mounted on a ceiling beam (not shown). The support angles 10 and 10 are fixed to each other, and the space between the support angles 10 and 10 is expandable / contractible so as to adapt to various lengths of the tank. Reference numeral 11 is a sprocket fitted to one shaft end of the hollow shaft 4, and the sprocket 11 can be rotated in both forward and reverse directions by a motor (not shown) via a chain 12.

In such an apparatus, as shown in FIG. 1, the coating is carried out by first coating the epoxy resin coating with the tank 1 in a state where the hollow shafts 4, 4 projecting at both ends thereof are horizontally supported via bearings 9. , The tank is filled with the coating solution consisting of solvent and water, and the tank is filled with the coating solution. The electrode 6 is the positive electrode and the tank 1 is the negative electrode. The inner surface is electrodeposited.

At that time, since the caps attached to the tank are all open, the electrodeposition coating is performed while the tank is also filled with the electrodeposition coating liquid, but some air remains in the tank. Therefore, in order to prevent this residual air 14 from hindering the contact between the inner surface of the tank and the electrodeposition coating liquid,
Through 12 and sprocket 11, as shown in FIG.
By rotating the tank 1 around the central axis, the inner surface of the tank is uniformly immersed in the coating liquid. The tanks may be rotated in the same direction, but in the case of the present embodiment, it is practically preferable to reciprocally rotate the tanks in the forward and reverse directions within an angle range of about 60 ° as shown by the arrow in the figure.

In order to electrodeposit the inner surface of the tank, it is convenient to immerse the entire tank in the coating bath at the same time as or before or after the inner surface coating, and also the outer surface of the tank is electrodeposited using the external electrodes. Because it is.

Here, except for the exposed part of the electrode 6, it is covered with an insulating film, and since the entire surfaces of the insulating bush 3 and the hollow shaft 4 are also covered with an insulating layer, only the exposed part of the electrode is coated. An electric current flows through the liquid to the inner surface of the tank, and the electric current 6 and the tank 1
No short-circuit current will flow due to direct contact with.

Further, depending on the size and structure of the tank, the electrodes are inserted into the caps of one end plate or the end caps of both end plates for electrodeposition coating.

The electrodeposition coating on the outer surface of the tank is performed in a known manner by providing the plate electrode 19 as a positive electrode in the electrodeposition coating bath so as to face the tank.

Although the electrodeposition coating current depends on the size and structure of the tank, for example, in the case of the inner surface coating of a 300φ × 700 single-chamber tank, as shown in FIG. 5, it becomes 15 A at an applied voltage of 300 V for about 20 s, and about 30 s. After reaching the peak of 30A, it decreases with the growth of the paint film and draws a mountain-shaped curve such as 12A in 1 min. This mountain-shaped curve is based on many experiments and achievements depending on the size and structure of the tank. , As a reference current curve.

Therefore, in the present invention, the coating current is detected by the detection device, and if the detected current at 20s after energization is within the permissible range of 15A ± α, and if the detected current at 1min after energization is within the permissible range of 12A ± β, then the coating is not performed. If it is normal and the detected current is out of the above allowable range, an alarm will be issued if the current is cut off via the relay. I do.

In the above embodiment, the one-chamber type tank is described.
Even in the two-chamber type and three-chamber type tanks shown in (B) and (C),
The both end chambers are electrodeposited using the caps in substantially the same manner as in the above embodiment, and the intermediate chambers are caps 2'attached to the side walls, respectively, as shown in FIG. After inserting the electrode 6'from the side, the electric power is supplied to the electrode 6'through an insulating cord while reversing the forward / reverse rotation around the horizontal axis in substantially the same manner as in the above embodiment. When the coating is performed, the coating condition can be monitored in the same manner as the above procedure.

〔The invention's effect〕

 According to such a method, the following effects can be obtained.

(1) Due to the normal electric field and current distribution formed between the electrode and the inner surface of the tank, the paint in the coating liquid is electrodeposited on the inner surface and / or the outer surface of the tank with a uniform thickness quickly and reliably.

(2) The electrode is supported by the insulating film, insulating bush and insulating hollow shaft on the outer periphery of the electrode, and the hollow shaft is supported by the insulating bearing.Therefore, a short circuit accident due to poor insulation between the electrode and the tank at the base insertion part. Electrodeposition coating is performed safely, and during internal electrodeposition coating, current does not flow from the electrodes to the outer surface of the tank through the coating liquid outside the tank.

(3) In the unlikely event that there is a circuit insulation failure, contact failure, etc., an alarm will be issued, so after investigating and repairing the defective part, further performing electrodeposition coating, observe it from the outside. It is possible to apply a uniform, smooth, strong and long-life coating even on difficult inner surfaces.

In short, according to the present invention, the rod-shaped electrode is inserted through the insulating bush on the central axis of the cylindrical tank whose both ends are closed by the end plates and / or the plate-shaped electrode is arranged facing the outside of the tank, and Fill the tank with electrodeposition coating liquid,
When the electrode is used as a positive electrode, the tank is used as a negative electrode, and a DC voltage is applied between the electrodes, the inner surface and / or the outer surface of the tank are electrodeposited. After determining the reference current curve as a reference by measuring the flowing electrodeposition coating current, based on the reference current curve, a reference current value having an allowable range in which the coating is normally performed on the tank at a predetermined time after the start of coating. Is set in advance, and then when the tank is sequentially electrodeposited, the electrodeposition coating current value flowing through the electrode and the tank when the predetermined time has elapsed is detected, and the detected value is within the allowable range of the reference current value. Economical cylindrical tank that quickly and reliably coats the inner and / or outer surface with a uniform thickness by distinguishing whether the electrodeposition coating is normal or abnormal by whether or not there is it. Since obtaining electrodeposition coating monitoring method, the present invention is extremely useful industrially.

[Brief description of drawings]

FIG. 1 is a side view showing a tank in an electrodeposition coating bath of one embodiment in which the present invention is applied to a one-chamber type air tank, and FIG.
FIG. 3 is a partial side view showing a supporting portion of the tank shown in FIG. 3, FIG. 3 is a partially enlarged vertical sectional view showing a bearing shown in FIG. 2, and FIG. 4 is a perspective view and a front view showing a pivoting point of the tank shown in FIG. FIG. 5 is a diagram showing changes over time in the electrodeposition current during the electrodeposition coating of the tank in FIG. 1, and FIG. 6 is a side view showing the electrodeposition coating and water washing / dehydration procedures of the intermediate chamber of the three-chamber air tank. Is. FIG. 7 is a longitudinal sectional view showing various structures of a known cylindrical air tank. DESCRIPTION OF SYMBOLS 1 ... Air tank (tank), 2 ... Base, 3 ... Insulating bush, 4 ... Hollow shaft, 6 ... Hollow rod-shaped electrode (electrode), 7 ... Nozzle hole, 8 ... Insulating film, 9 ... Bearing, 10 ... Support angle, 11
… Sprocket, 12… Chain, 14… Residual air

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kimoro Murata 26-3-3, Nagatahigashi, Minami-ku, Yokohama-shi, Kanagawa (56) References JP-B-45-19593 (JP, B1)

Claims (1)

[Claims] 1. A rod-shaped electrode is inserted through an insulating bush on a central axis of a cylindrical tank whose both ends are closed by end plates and / or a plate-shaped electrode is arranged so as to face the outside of the tank. Elapsed time from the start of coating when a coating current flows when the inside and / or outside of the tank is electrodeposited by applying a DC voltage between the electrodes with the electrode serving as the positive electrode and the tank serving as the negative electrode with an electrodeposition coating liquid. After the electrodeposition coating current flowing through the electrode and the tank, which changes with it, is measured and a reference current curve as a reference is determined, the coating is normally performed on the tank at a predetermined time after the start of coating based on the reference current curve. The reference current value having an allowable range is preset, and then the electrodeposition coating current value flowing through the electrodes and the tank when the predetermined time has elapsed when the tank is sequentially electrodeposition coated, Electrodeposition coating monitoring method of a cylindrical tank, wherein the detection value of it is determined normal or abnormal tolerance within whether by electrodeposition coating in the reference current value.