Avoiding rust inside zinc plated steel tube

A. Nickel-chrome plated tubing is sometimes phosphatized after plating and before unracking to solve this problem. But I don't know if a phosphate chemistry can be found that will be compatible with the alkaline zinc plating and any chromate that you may be applying to it.

A. A water soluble rust preventive in your final rinse will provide moderate rust prevention.

A. A lacquer topcoat applied by immersion after plating will offer some degree of protection against rusting.

A. Electrical wiring conduit is painted on the inside with an automatic rig that goes all the way through the 10 foot long 3/4 inch tube!

A. Try to maintain bath composition 10 gm metal and 100 gm caustic with good brightener system, with some solution movement may improve inner zinc plating there by you protect corrosion.internal ms anode is ideal even achieving thickness of 2 to 4 micron zinc inside. In India we are doing tubes up to 20 feet with proper inner coverage with alkaline bath chemistry.

A. Skip electroplating and just use hot dip galvanizing?

A. Dear Thomas.

You really provide an answer, that has made my ordinary day at work a little more pleasant; after a long, long time smile has come on my face :)
But none the less, I rather wear rubber gloves than asbestos one :)

Nice day to all of you from Slovenia!

A. Dear Sir,

In Chennai we plate 20 feet length tube with 3/4 inch dia and some times 1/2 inch. This tube is a fuel conducting tube for major automobile heavy vehicle manufacturer. Bath chemistry as I already mentioned 10 to 12 gm metal 100 to 120 caustic. With good world no one brightener system. Also we provide internal 2 mm to 3mm auxiliary ms anode with pp bushes, we had jig designed in such a way in each jig 6 tubes were loaded with solution movement. Also we maintain higher addition rate of brightener and we use some booster for extra throwing. This system we are running for last 4 years consistently without any problem. Earlier we used cyanide base bath. Use of good inhibiter in acid and post rinse with 7 to 8 pH water, bright dip we use .5% to 1% nitric acid, chromate we use hexavalent yellow. No sealer, no lacquer.

With best regards.

A. Hi Hemant,

We plated power steering tubes for several years where NO plating was allowed on the internal, as platers we find that murphy's laws as well as faraday's always seem to come into play, we found the best solution was to use a Macdermid product called "ferrohib" which is water soluble this provided enough protection until the part was assembled.

A. This is always a major concern with tubing, particularly the longer the tube gets. The looming questions are typically to plug or not to plug, what to apply after plating and how? We plate tubing from very short pieces up to 21 feet in length. The best solution is a rust inhibiting post-dip, which does fairly well for the short term. Other methods such as spraying an inhibitor through the tube is a more time consuming and messy method, often leaving an unwanted appearance on the outside of the tubing.

A. Hi Balasubramani. Please email a pic of the part to mooney@finishing.com and tell us whether you are rack or barrel plating, using acid, alkaline, or cyanide zinc, and perhaps the dimensions of this "slot". Usually there are answers but not easy answers :-)

Regards,

A. We are now doing plating fuel pipes of 15, 18 & 25 diameter and length up to 4000 mm for Automobile industry. We are able to provide coating on inner and outer dia of pipes of almost 8-10 mm thickness. Solution for inner plating is there and very much successful.

  Hi Allen. Glad to hear it! By all means publicly share what you can afford to on this mutual help forum (or contact us about advertising your services).

Regards,