|Content Type||Conference Paper|
|Title||FUNDAMENTALS OF BRISTLE BLASTING PROCESS FOR REMOVING CORROSIVE LAYER|
|Authors||Robert J.Stango, Piyush Khullar, Mechanical Engineering Department|
|Source||CORROSION 2009, March 22 - 26, 2009 , Atlanta, GA|
|Copyright||2009. NACE International|
|Keywords||Bristle Blast; Surface Cleaning; Surface Preparation; Removal of Corrosive Products; Corrosion Removal; Anchor Profile|
This technical paper introduces a newly developed surface preparation process termed bristle blasting, which utilizes a specially designed rotary power tool for simultaneously removing corrosion and generating an anchor profile. The process derives its name from sharp, hardened bristle tips which, upon striking the corroded surface, immediately retract, thereby creating a micro-indentation that both removes corrosion and simultaneously exposes fresh subsurface material. Consequently, the repeated collision/retraction of bristle tips with the corroded surface leads to a surface cleanliness and anchor profile that resembles surface prepared by grit blasting processes. Performance of the bristle blasting process is evaluated within the context of an application that involves cleaning/texturing severely corroded API 5L piping, which is commonly used for onshore/offshore petroleum transport applications. The results demonstrate that surface cleanliness and texture achieved via bristle blasting tools is on a par with grit blasting processes. That is, a nearwhite metal and white metal appearance of cleaned surfaces is routinely obtained, and is accompanied by an average peak-to-valley surface texture (Rz, microns) given by: 83 ≥ Rz ≥ 62. Finally, careful study indicates that bristle blasting tools can remove corrosion at a rate in excess of one square meter per hour throughout the duration of tool life.
INTRODUCTION AND BACKGROUND:
Steel structures play a vital role in supporting the infrastructure of transportation, habitat, and the distribution of goods and natural resources. In order to safeguard and maintain this infrastructure, polymer chemists have formulated advanced paints and coatings that can protect surfaces from corrosion and prolong the life/integrity of steel components. Nevertheless, these coatings are subject to environmental attack and eventually deteriorate, thereby requiring partial or complete removal prior to the reapplication of fresh coating. This cycle of repair/refurbishment is an important part of infrastructure maintenance programs that is both costly and time consuming. Although grit blasting is the most widely used method for preparing steel surfaces, maintenance engineers are constantly searching for new/alternative surface treatment processes that can circumvent many of the difficulties and shortcomings that are associated with this process. Most notably, for example, grit blasting is an expensive, cumbersome process that is neither environment nor userfriendly. The seriousness of health and safety issues has recently prompted the Environmental Protection Agency (USA) to propose national emission standards for controlling hazardous air pollutants associated with abrasive blasting1. Occupational Safety and Health Administration (USA) has recently issued directives that may have widespread implications on nearly all types of abrasive blasting processes/media2. Altogether, these concerns render the abrasive blasting process especially inefficient and poorly suited for applications involving local rehabilitation or “spotrepair”, wherein steel surfaces are in need of immediate repair due to paint delamination and/or severe corrosion. In this paper, a new process termed bristle blasting is introduced that utilizes a rotary power tool for simultaneously removing corrosion and generating an anchor profile. Although the bristle blasting tool has an appearance that resembles wire brushes, the underlying principles of operation are shown to have little, if any, commonality with brushing processes.
|File Size||1002 KB||13|