Panel Provides Answers to Queries About Tank Truck Corrosion Issues
Feb 1, 1999 12:00 PM
Five representatives of the tank truck industry agree that tank corrosion is never-ending and often insidious, but they refuse to be complacent. They offered helpful advice at the Cargo Tank Maintenance Seminar sponsored by the National Tank Truck Carriers October 19-21 in Chicago, Illinois.
The panel included Al Hendricks, Plasite Protective Coatings, moderator; Chuck Boudin, Montgomery Tank Lines; Alain Chatillon, Tankcon FRP Inc; Lee Robinson, Arbonite Coatings & Linings; and Fred Suess, Technimet Corporation.
The panel answered numerous questions, often joined by members of the audience, about tank corrosion, including these:
Question: How effective are the chemical tables?
Answer: Although tables for specific products are accurate, there may be an additional substance in the product that is unknown at the time of shipment. Tests are available that will determine all product content and if the products are compatible with certain elements, such as stainless steel. However, variations in temperatures and time in the trailer may set up chemical reactions. Temperature fluctuations at loading can affect the product. Also to be taken into consideration are other products being hauled in the trailer, what chemicals are used when it is cleaned, and the possible reactions between products and the heel left after washing.
Question: Whose responsibility is it to supply details on the product's content and to test for corrosion potential?
Answer: The shipper. 49CFR makes it clear, but applies only to hazardous materials. Other seemingly benign products can cause problems as well. However, it is essential to maintain good communications with the shipper and to be sure information is current and accurate.
Question: How can a carrier be sure equipment is protected?
Answer: If the carrier wants to be sure that equipment is protected, maintenance personnel must be trained to detect corrosion. Experienced tank inspectors and a comprehensive program of inspection are especially important so that any damage can be pinpointed.
Question: Are there tools to measure pitting?
Answer: Yes, but they can be expensive. Some cost as much as $2,000.
Question: What are ways to repair pits?
Answer: In general, pitting should be repaired as soon as possible after discovery. Buffing can remove minor pitting, but deep pits usually are welded over. All welds should be polished smooth, acid cleaned, and the entire area passivated to help avoid future problems.
Question: Should stainless steel tanks be air-dried after cleaning?
Answer: Yes, if they are left to stand more than 24 hours. Bacteria, a corroding slime that attacks stainless steel rapidly and causes pitting, can form.
Question: What can be done in areas where manhole linings have chipped away?
Answer: There are collar protectors available that protect that area. Watch for damage done at cleaning facilities. Cleaning detergents can damage hardware. If damage is caught early, it can be repaired.
Question: Is a CT number required for lining shops?
Answer: The number is not needed to apply linings, but is required to conduct testing.
Question: What other alloys are available for tank construction?
Answer: There are others. Some are expensive, some difficult to use in the manufacturing process. But there is nothing that is resistant to all chemical products.
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